### FFmpeg Core Initialization and Setup (C)

Source: https://ffmpeg.org/doxygen/8.0/qsv__transcode_8c

This C code snippet includes necessary headers for FFmpeg operations, covering AVUtil, AVCodec, and AVFormat. It sets up the foundation for interacting with FFmpeg's multimedia functionalities, potentially for encoding, decoding, or format handling. It's a common starting point for FFmpeg applications.

```C
#include <stdio.h>
#include <errno.h>
#include <libavutil/hwcontext.h>
#include <libavutil/mem.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavutil/opt.h>
```

--------------------------------

### FFmpeg Initialization and Setup Functions (C)

Source: https://ffmpeg.org/doxygen/8.0/libswscale_2utils_8c_source

Contains cold initialization functions for RGB to RGB conversion and range conversion logic. These are typically called once at the start of processing.

```c
av_cold void ff_sws_rgb2rgb_init(void)
// Definition: rgb2rgb.c:141

av_cold void ff_sws_init_range_convert(SwsInternal *c)
// Definition: swscale.c:622
```

--------------------------------

### JACK Audio Interface Setup

Source: https://ffmpeg.org/doxygen/8.0/jack_8c_source

Functions and structures related to the JACK Audio Connection Kit interface within FFmpeg. This includes starting the JACK client (`start_jack`), handling XRUN callbacks (`xrun_callback`, `process_callback`), and managing JACK-specific data structures (`JackData`).

```c
static int start_jack(AVFormatContext *context)
**Definition:** jack.c:149
```

```c
static int xrun_callback(void *arg)
**Definition:** jack.c:123
```

```c
static int process_callback(jack_nframes_t nframes, void *arg)
**Definition:** jack.c:60
```

```c
JackData
**Definition:** jack.c:44
```

--------------------------------

### Build System Commands for FFmpeg

Source: https://ffmpeg.org/doxygen/8.0/bin2c_8c_source

Documents various make commands for building FFmpeg, including preprocessing assembler files, setting installation destinations, generating references, running regression tests (FATE), building examples, checking headers, and creating fuzzers for decoders and bitstream filters. It also covers parallel builds and error handling.

```makefile
DBG Preprocess x86 external assembler files to a dbg asm file in the object which then gets compiled Helps in developing those assembler files
DESTDIR Destination directory for the install useful to prepare packages or install FFmpeg in cross environments
GEN Set to ‘1’ to generate the missing or mismatched references
Makefile builds all the libraries and the executables
fate Run the fate test note that you must have installed it
fate list List all fate regression test targets
fate list failing List the fate tests that failed the last time they were executed
fate clear reports Remove the test reports from previous test libraries and programs
examples Build all examples located in doc examples
checkheaders Check headers dependencies
alltools Build all tools in tools directory
tools target_dec_< decoder > _fuzzer Build fuzzer to fuzz the specified decoder
tools target_bsf_< filter > _fuzzer Build fuzzer to fuzz the specified bitstream filter
Useful standard make this is useful to reduce unneeded rebuilding when changing but note that you must force rebuilds of files that actually need it by hand then make j< num > Rebuild with multiple jobs at the same time Faster on multi processor systems
make k Continue build in case of errors

```

--------------------------------

### RV34 Get Start Offset

Source: https://ffmpeg.org/doxygen/8.0/rv34_8h

Retrieves the start offset for decoding macroblocks.

```APIDOC
## GET /api/rv34/get_start_offset

### Description
Retrieves the start offset for decoding macroblocks in the RV34 decoder. This function is part of the common decoding utilities.

### Method
GET

### Endpoint
/api/rv34/get_start_offset

### Parameters
#### Path Parameters
None

#### Query Parameters
- **gb** (GetBitContext *) - Required - Pointer to the GetBitContext.
- **blocks** (int) - Required - The number of blocks.

### Request Example
```json
{
  "gb": "<GetBitContext_pointer>",
  "blocks": 16
}
```

### Response
#### Success Response (200)
- **return_value** (int) - The calculated start offset.

#### Response Example
```json
{
  "return_value": 32
}
```
```

--------------------------------

### init_setup_shader

Source: https://ffmpeg.org/doxygen/8.0/ffv1enc__vulkan_8c

Initializes the setup shader.

```APIDOC
## init_setup_shader

### Description
Initializes the setup shader.

### Method
`static int init_setup_shader(AVCodecContext * _avctx_, FFVkSPIRVCompiler * _spv_)
`

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (0)
Returns 0 on success.

#### Response Example
None
```

--------------------------------

### Get GUID (C)

Source: https://ffmpeg.org/doxygen/8.0/riff_8h

Reads a GUID from an AVIOContext and stores it in an ff_asf_guid structure. This function is essential for parsing ASF files and other formats that use GUIDs to identify chunks or stream properties.

```c
int ff_get_guid(
    AVIOContext *_s_,
    ff_asf_guid *_g_
);
```

--------------------------------

### MPEG Video Frame Start Initialization

Source: https://ffmpeg.org/doxygen/8.0/mpegvideo__dec_8c_source

A generic function called after decoding the header and before decoding a frame. It performs necessary setup for the start of frame processing. Requires MpegEncContext and AVCodecContext pointers.

```c
int ff_mpv_frame_start(MpegEncContext *s, AVCodecContext *avctx)
```

--------------------------------

### FFmpeg Tool Initialization (C)

Source: https://ffmpeg.org/doxygen/8.0/zmqsend_8c_source

This snippet shows the initialization of a tool within FFmpeg, including header includes for configuration, standard I/O, string manipulation, and ZeroMQ. It also includes libavutil headers for logging, memory management, and buffer printing. Conditional includes for unistd.h are present for getopt.

```c
#include "config.h"

#include <stdio.h>
#include <string.h>
#include <zmq.h>

#include "libavutil/log.h"
#include "libavutil/mem.h"
#include "libavutil/bprint.h"

#if HAVE_UNISTD_H
#include <unistd.h> /* getopt */
#endif

#if !HAVE_GETOPT

```

--------------------------------

### Getting GUID Information with ff_get_guid

Source: https://ffmpeg.org/doxygen/8.0/riffdec_8c_source

Reads a GUID (Globally Unique Identifier) structure from an AVIOContext. GUIDs are often used in media file formats to identify specific data chunks or codecs.

```c
int ff_get_guid(AVIOContext *s, ff_asf_guid *g)

```

--------------------------------

### GUID Handling - FFmpeg

Source: https://ffmpeg.org/doxygen/8.0/riff_8h

Contains functions for getting, putting, and comparing GUIDs (Globally Unique Identifiers), which are used in formats like ASF. It also includes macros for defining and formatting GUIDs, as well as predefined base GUIDs for various media types.

```c
typedef uint8_t ff_asf_guid[16];

static av_always_inline int ff_guidcmp (const void *g1, const void *g2)
{
    /* ... implementation ... */
    return comparison_result;
}

int ff_get_guid (AVIOContext *s, ff_asf_guid *g)
{
    /* ... implementation ... */
    return success_or_error;
}

void ff_put_guid (AVIOContext *s, const ff_asf_guid *g)
{
    /* ... implementation ... */
}

const ff_asf_guid * ff_get_codec_guid (enum AVCodecID id, const AVCodecGuid *av_guid)
{
    /* ... implementation ... */
    return guid_pointer;
}

enum AVCodecID ff_codec_guid_get_id (const AVCodecGuid *guids, ff_asf_guid guid)
{
    /* ... implementation ... */
    return codec_id;
}

#define FF_PRI_GUID "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x%02x%02x "
#define FF_ARG_GUID g[0], g[1], g[2], g[3], g[4], g[5], g[6], g[7], g[8], g[9], g[10], g[11], g[12], g[13], g[14], g[15], g[3], g[2], g[1], g[0], g[5], g[4], g[7], g[6], g[8], g[9], g[10], g[11], g[12], g[13], g[14], g[15]

#define FF_MEDIASUBTYPE_BASE_GUID 0x00, 0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0xAA, 0x00, 0x38, 0x9B, 0x71
#define FF_AMBISONIC_BASE_GUID 0x21, 0x07, 0xD3, 0x11, 0x86, 0x44, 0xC8, 0xC1, 0xCA, 0x00, 0x00, 0x00
#define FF_BROKEN_BASE_GUID 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0xAA
```

--------------------------------

### Main Function Example (C)

Source: https://ffmpeg.org/doxygen/8.0/tests_2camellia_8c

Demonstrates the entry point of the FFmpeg application, typically handling command-line arguments. This function is defined in the camellia.c file.

```c
#include <stddef.h>
#include <string.h>
#include "libavutil/camellia.h"
#include "libavutil/log.h"
#include "libavutil/mem.h"

/**
 * @brief Main function entry point.
 *
 * @param argc Number of command-line arguments.
 * @param argv Array of command-line argument strings.
 * @return 0 on success, a negative value on error.
 */
int main(int argc, char *argv[]) {
    // Function implementation would go here
    return 0;
}
```

--------------------------------

### Initialization and Utility Functions

Source: https://ffmpeg.org/doxygen/8.0/audioconvert_8c

This snippet includes various initialization and utility functions, such as initializing offsets, samples, and checking for image availability. These are common setup and state management functions.

```c
init();
init_offset();
init_sample();
image_available();
```

--------------------------------

### Get Codec ID from GUID - C

Source: https://ffmpeg.org/doxygen/8.0/riffdec_8c

Maps an ASF (Advanced Systems Format) GUID to an AVCodecID. This function is used to determine the codec associated with a specific GUID encountered during file parsing, enabling FFmpeg to correctly interpret the media data. It requires a list of GUID mappings and the target GUID.

```c
enum AVCodecID ff_codec_guid_get_id(const AVCodecGuid *_guids, ff_asf_guid _guid)
```

--------------------------------

### FFmpeg Filter Initialization Example (C)

Source: https://ffmpeg.org/doxygen/8.0/vf__removegrain_8c

Demonstrates the initialization process for filters within the FFmpeg libavfilter library. It includes necessary header files for image utilities, options, pixel descriptions, sorting, and filter definitions. This snippet highlights the setup required before applying video filtering operations.

```c
#include "libavutil/imgutils.h"
#include "libavutil/opt.h"
#include "libavutil/pixdesc.h"
#include "libavutil/qsort.h"
#include "avfilter.h"
#include "filters.h"
#include "removegrain.h"
#include "video.h"

```

--------------------------------

### QSV Transcoding API Usage Example (C)

Source: https://ffmpeg.org/doxygen/8.0/qsv__transcode_8c_source

This C code snippet is the main example for QSV-accelerated transcoding. It parses command-line arguments to set up input and output files, codec, and initial encoder options. It also handles dynamic changes to encoder parameters during the transcoding process. Dependencies include libavutil, libavcodec, and libavformat.

```c
/**
 * @file Intel QSV-accelerated video transcoding API usage example
 * @example qsv_transcode.c
 *
 * Perform QSV-accelerated transcoding and show to dynamically change
 * encoder's options.
 *
 * Usage: qsv_transcode input_stream codec output_stream initial option
 * { frame_number new_option }
 * e.g: - qsv_transcode input.mp4 h264_qsv output_h264.mp4 "g 60"
 * - qsv_transcode input.mp4 hevc_qsv output_hevc.mp4 "g 60 async_depth 1"
 * 100 "g 120"
 * (initialize codec with gop_size 60 and change it to 120 after 100
 * frames)
 */

#include <stdio.h>
#include <errno.h>

#include <libavutil/hwcontext.h>
#include <libavutil/mem.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavutil/opt.h>

static AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
static AVBufferRef *hw_device_ctx = NULL;
static AVCodecContext *decoder_ctx = NULL, *encoder_ctx = NULL;
static int video_stream = -1;

typedef struct DynamicSetting {
    int frame_number;
    char* optstr;
} DynamicSetting;
static DynamicSetting *dynamic_setting;
static int setting_number;
static int current_setting_number;

static int str_to_dict(char* optstr, AVDictionary **opt)
{
    char *key, *value;
    if (strlen(optstr) == 0)
        return 0;
    key = strtok(optstr, " ");
    if (key == NULL)
        return AVERROR(EINVAL);
    value = strtok(NULL, " ");
    if (value == NULL)
        return AVERROR(EINVAL);
    av_dict_set(opt, key, value, 0);
    do {
        key = strtok(NULL, " ");
        if (key == NULL)
            return 0;
        value = strtok(NULL, " ");
        if (value == NULL)
            return AVERROR(EINVAL);
        av_dict_set(opt, key, value, 0);
    } while(1);
}

static int dynamic_set_parameter(AVCodecContext *avctx)
{
    AVDictionary *opts = NULL;
    int ret = 0;
    static int frame_number = 0;
    frame_number++;
    if (current_setting_number < setting_number &&
        frame_number == dynamic_setting[current_setting_number].frame_number) {
        AVDictionaryEntry *e = NULL;
        ret = str_to_dict(dynamic_setting[current_setting_number++].optstr, &opts);
        if (ret < 0) {
            fprintf(stderr, "The dynamic parameter is wrong\n");
            goto fail;
        }
        /* Set common option. The dictionary will be freed and replaced
         * by a new one containing all options not found in common option list.
         * Then this new dictionary is used to set private option. */
        if ((ret = av_opt_set_dict(avctx, &opts)) < 0)
            goto fail;
        /* Set codec specific option */
        if ((ret = av_opt_set_dict(avctx->priv_data, &opts)) < 0)
            goto fail;
        /* There is no "framerate" option in common option list. Use "-r" to set
         * framerate, which is compatible with ffmpeg commandline. The video is
         * assumed to be average frame rate, so set time_base to 1/framerate. */
        e = av_dict_get(opts, "r", NULL, 0);
        if (e) {
            avctx->framerate = av_d2q(atof(e->value), INT_MAX);
            encoder_ctx->time_base = av_inv_q(encoder_ctx->framerate);
        }
    }
fail:
    av_dict_free(&opts);
    return ret;
}

static int get_format(AVCodecContext *avctx, const enum AVPixelFormat *pix_fmts)
{
    while (*pix_fmts != AV_PIX_FMT_NONE) {
        if (*pix_fmts == AV_PIX_FMT_QSV) {
            return AV_PIX_FMT_QSV;
        }

        pix_fmts++;
    }

    fprintf(stderr, "The QSV pixel format not offered in get_format()\n");

    return AV_PIX_FMT_NONE;
}

static int open_input_file(char *filename)
{
    int ret;
    const AVCodec *decoder = NULL;
    AVStream *video = NULL;

    if ((ret = avformat_open_input(&ifmt_ctx, filename, NULL, NULL)) < 0) {
        fprintf(stderr, "Cannot open input file '%s', Error code: %s\n",
                filename, av_err2str(ret));
        return ret;
    }

    if ((ret = avformat_find_stream_info(ifmt_ctx, NULL)) < 0) {
        fprintf(stderr, "Cannot find input stream information. Error code: %s\n",
                av_err2str(ret));
        return ret;
    }

    ret = av_find_best_stream(ifmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
    if (ret < 0) {
        fprintf(stderr, "Cannot find a video stream in the input file. "
                "Error code: %s\n", av_err2str(ret));
        return ret;
    }
    video_stream = ret;
    video = ifmt_ctx->streams[video_stream];

    switch(video->codecpar->codec_id) {
    case AV_CODEC_ID_H264:
        decoder = avcodec_find_decoder_by_name("h264_qsv");
        break;
    case AV_CODEC_ID_HEVC:
        decoder = avcodec_find_decoder_by_name("hevc_qsv");
        break;
    case AV_CODEC_ID_VP9:
        decoder = avcodec_find_decoder_by_name("vp9_qsv");
        break;
    case AV_CODEC_ID_VP8:
        decoder = avcodec_find_decoder_by_name("vp8_qsv");
        break;
    case AV_CODEC_ID_AV1:
        decoder = avcodec_find_decoder_by_name("av1_qsv");
        break;
    case AV_CODEC_ID_MPEG2VIDEO:
        decoder = avcodec_find_decoder_by_name("mpeg2_qsv");
        break;
    case AV_CODEC_ID_MJPEG:
        decoder = avcodec_find_decoder_by_name("mjpeg_qsv");
        break;
    default:
        break;
    }
    return 0;
}

```

--------------------------------

### MPEG2 Get Frame Start

Source: https://ffmpeg.org/doxygen/8.0/vaapi__mpeg2_8c

Determines the start of a frame for MPEG2 decoding, specifically for field pictures or frame pictures.

```APIDOC
## GET mpeg2_get_is_frame_start

### Description
Determines frame start: first field for field picture or frame picture.

### Method
STATIC

### Endpoint
N/A (Internal function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
- **int** - 1 if it's the start of a frame, 0 otherwise.

#### Response Example
```json
{
  "is_frame_start": 1
}
```

### Function Signature
`static int mpeg2_get_is_frame_start(const MpegEncContext *s)`
```

--------------------------------

### Get GUID from AVIOContext - C

Source: https://ffmpeg.org/doxygen/8.0/riff_8h_source

Reads a 16-byte GUID (Globally Unique Identifier) from an AVIOContext and stores it in the provided ff_asf_guid buffer.

```c
int ff_get_guid(AVIOContext *s, ff_asf_guid *g);
```

--------------------------------

### FFmpeg Licensing and Includes

Source: https://ffmpeg.org/doxygen/8.0/x86_2idctdsp__init_8c_source

This code snippet includes the standard FFmpeg license information and necessary header files for libavcodec and x86-specific CPU functionalities. It sets up the build environment for FFmpeg components.

```c
/*
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "config.h"
#include "libavutil/attributes.h"
#include "libavutil/cpu.h"
#include "libavutil/x86/cpu.h"
#include "libavcodec/avcodec.h"
#include "libavcodec/idctdsp.h"
#include "idctdsp.h"
#include "simple_idct.h"

/* Input permutation for the simple_idct_mmx */
```

--------------------------------

### FFmpeg Core Initialization and Filter Setup C

Source: https://ffmpeg.org/doxygen/8.0/decode__filter__audio_8c

This snippet demonstrates the core setup for FFmpeg processing, including opening input files, initializing filter graphs, and setting up buffer sources and sinks. It requires FFmpeg's libavformat, libavcodec, and libavfilter libraries.

```c
#include <unistd.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>
#include <libavutil/channel_layout.h>
#include <libavutil/mem.h>
#include <libavutil/opt.h>

static const char *filter_descr = "aresample=8000,aformat=sample_fmts=s16:channel_layouts=mono";
static const char *player = "ffplay -f s16le -ar 8000 -ac 1 -";
static AVFormatContext *fmt_ctx;
static AVCodecContext *dec_ctx;
AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;
static int audio_stream_index = -1;

static int open_input_file (const char *filename)
{
    // Implementation details for opening input file
    return 0;
}

static int init_filters (const char *filters_descr)
{
    // Implementation details for initializing filters
    return 0;
}

static void print_frame (const AVFrame *frame)
{
    // Implementation details for printing frame data
}

int main (int argc, char **argv)
{
    // Main function logic, likely calling open_input_file and init_filters
    return 0;
}
```

--------------------------------

### Get Codec GUID (C)

Source: https://ffmpeg.org/doxygen/8.0/riff_8h

Retrieves the ASF GUID corresponding to a given FFmpeg AVCodecID and AVCodecGuid structure. This function is used when writing headers for ASF files to map codec types to their respective GUIDs.

```c
const ff_asf_guid* ff_get_codec_guid(
    enum AVCodecID _id_,
    const AVCodecGuid *_av_guid_
);
```

--------------------------------

### Get Byte Context Buffer Start

Source: https://ffmpeg.org/doxygen/8.0/prores__raw_8c_source

Provides access to the starting pointer of the buffer managed by the GetByteContext. This is fundamental for reading data from the bytestream.

```c
const uint8_t * buffer_start;

```

--------------------------------

### Setup VP8 Partitions

Source: https://ffmpeg.org/doxygen/8.0/vp8_8c

Sets up the partitions for VP8 decoding. Takes a VP8 context, buffer, and buffer size as input. Defined in vp8.c.

```c
static int setup_partitions(VP8Context *_s, const uint8_t *_buf, int _buf_size_)
```

--------------------------------

### COOK Initialization and Setup

Source: https://ffmpeg.org/doxygen/8.0/cook_8c_source

Functions for initializing and setting up the COOK codec context, including gain tables and windowing functions.

```c
static av_cold void init_gain_table(COOKContext *q)
static const uint8_t envelope_quant_index_huffcounts[13][16]
static const uint8_t envelope_quant_index_huffsyms[13][24]
```

--------------------------------

### Get Codec GUID - FFmpeg RIFF

Source: https://ffmpeg.org/doxygen/8.0/riff_8h_source

Retrieves the AVCodecGuid for a given AVCodecID. This function is used to map codec IDs to their corresponding GUIDs, which are often used in RIFF-based formats like ASF. It takes an AVCodecID and a list of GUIDs.

```c
const ff_asf_guid * ff_get_codec_guid(enum AVCodecID id, const AVCodecGuid *av_guid)
{
    // ... implementation ...
    return NULL;
}
```

--------------------------------

### Get Segment Start Time from Timeline

Source: https://ffmpeg.org/doxygen/8.0/dashdec_8c

A static function that calculates the start time of a segment based on its timeline information. It requires a pointer to a `representation` struct and the current sequence number, returning the start time as `int64_t`.

```c
static int64_t get_segment_start_time_based_on_timeline(struct representation *_pls_, int64_t _cur_seq_no_)
```

--------------------------------

### FFmpeg Build System Options

Source: https://ffmpeg.org/doxygen/8.0/avio__http__serve__files_8c_source

Documents various standard make targets and options for building FFmpeg, including cross-compilation, testing, and tool generation. Includes options for preprocessing assembler files and setting installation directories.

```text
Makefile the full command issued by make and its output will be shown on the screen DBG Preprocess x86 external assembler files to a dbg asm file in the object which then gets compiled Helps in developing those assembler files DESTDIR Destination directory for the install useful to prepare packages or install FFmpeg in cross environments GEN Set to ‘1’ to generate the missing or mismatched references Makefile builds all the libraries and the executables fate Run the fate test note that you must have installed it fate list List all fate regression test targets fate list failing List the fate tests that failed the last time they were executed fate clear reports Remove the test reports from previous test libraries and programs examples Build all examples located in doc examples checkheaders Check headers dependencies alltools Build all tools in tools directory config Reconfigure the project with the current configuration tools target_dec_< decoder > _fuzzer Build fuzzer to fuzz the specified decoder tools target_bsf_< filter > _fuzzer Build fuzzer to fuzz the specified bitstream filter Useful standard make this is useful to reduce unneeded rebuilding when changing headers
```

--------------------------------

### Initialize FFmpeg Guided Filter (C)

Source: https://ffmpeg.org/doxygen/8.0/vf__guided_8c_source

Initializes the FFmpeg guided filter by setting up input pads. It configures a 'source' video input pad and an optional 'guidance' video input pad if guidance mode is enabled. Returns an error code if pad setup fails.

```c
static av_cold int init(AVFilterContext *ctx)
{
    GuidedContext *s = ctx->priv;
    AVFilterPad pad = { 0 };
    int ret;

    pad.type = AVMEDIA_TYPE_VIDEO;
    pad.name = "source";
    pad.config_props = config_input;

    if ((ret = ff_append_inpad(ctx, &pad)) < 0)
        return ret;

    if (s->guidance == ON) {
        pad.type = AVMEDIA_TYPE_VIDEO;
        pad.name = "guidance";
        pad.config_props = NULL;

        if ((ret = ff_append_inpad(ctx, &pad)) < 0)
            return ret;
    }

    return 0;
}
```

--------------------------------

### Main Function for FFmpeg Example

Source: https://ffmpeg.org/doxygen/8.0/tests_2movenc_8c_source

The main entry point of the program. It parses command-line arguments, initializes FFmpeg structures like MD5 context and AVPacket, and then proceeds to create fragmented media files with non-empty moov atom.

```c
int main(int argc, char **argv)
{
int c;
uint8_t header[HASH_SIZE];
uint8_t content[HASH_SIZE];
int empty_moov_pos;
int prev_pos;

for (;;)
{
c = getopt(argc, argv, "wh");
if (c == -1)
break;
switch (c) {
case 'w':
write_file = 1;
break;
default:
case 'h':
help();
return 0;
}
}

md5 = av_md5_alloc();
if (!md5)
return 1;
pkt = av_packet_alloc();
if (!pkt) {
av_free(md5);
return 1;
}

// Write a fragmented file with an initial moov that actually contains some
// samples. One moov+mdat with 1 second of data and one moof+mdat with 1
// second of data.
init_out("non-empty-moov");
av_dict_set(&opts, "movflags", "+frag_keyframe", 0);
init(0, 0);
mux_gops(2);
finish();
close_out();
}
```

--------------------------------

### Constant for ASF Stream Header GUID

Source: https://ffmpeg.org/doxygen/8.0/asfenc_8c_source

This constant, ff_asf_stream_header, holds the GUID for the stream header in ASF files. It's used to identify the start of stream-specific information.

```c
const ff_asf_guid ff_asf_stream_header
```

--------------------------------

### Bink Audio Context Initialization and Callback Pointers

Source: https://ffmpeg.org/doxygen/8.0/binkaudio_8c_source

Sets up the Bink audio decoder's core callbacks and capabilities within the FFCodec structure.

```c
static const FFCodec decoder = {
    .priv_data_size = sizeof(BinkAudioContext),
    .init = decode_init,
    .flush = decode_flush,
    .close = decode_end,
    FF_CODEC_RECEIVE_FRAME_CB(binkaudio_receive_frame),
    .p.capabilities = AV_CODEC_CAP_DR1,
    .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
};
```

--------------------------------

### FFmpeg Get GUID Function

Source: https://ffmpeg.org/doxygen/8.0/asfdec__o_8c_source

Reads a Globally Unique Identifier (GUID) from an AVIOContext. This is often used in file format parsing, like RIFF or ASF.

```c
int ff_get_guid(AVIOContext *s, ff_asf_guid *g)
{
    // Implementation to read a GUID
    return 0; // Placeholder
}
```

--------------------------------

### Get Codec GUID (C)

Source: https://ffmpeg.org/doxygen/8.0/riffenc_8c_source

Retrieves the GUID (Globally Unique Identifier) associated with a specific AVCodecID. This is often used in container formats like ASF for codec identification.

```c
const ff_asf_guid * ff_get_codec_guid(enum AVCodecID id, const AVCodecGuid *av_guid)
**Definition:** riffenc.c:365
```

--------------------------------

### FFmpeg Initialization and Setup Functions

Source: https://ffmpeg.org/doxygen/8.0/vp9dsp__template_8c

Functions for initializing various components and data structures within FFmpeg, including decoders, patterns, and tables.

```c
init();
init_bio_method();
init_decoder();
init_demo();
init_dimensions();
init_dxgi_dda();
init_pattern_from_file();
init_slice();
init_slice_c();
init_table_pools();
```

--------------------------------

### Get Codec GUID FFmpeg C

Source: https://ffmpeg.org/doxygen/8.0/riffenc_8c_source

Retrieves the FFmpeg ASF GUID for a given AVCodecID from a provided array of AVCodecGuid structures. It iterates through the array to find a matching codec ID. Returns a pointer to the GUID or NULL if not found. Dependencies include av_assert0 and AVCodecID.

```c
const ff_asf_guid *ff_get_codec_guid(enum AVCodecID id, const AVCodecGuid *av_guid)
{
 int i;
 for (i = 0; av_guid[i].id != AV_CODEC_ID_NONE; i++) {
 if (id == av_guid[i].id)
 return &(av_guid[i].guid);
 }
 return NULL;
}
```

--------------------------------

### Initialize Decoder Context with Hardware Acceleration

Source: https://ffmpeg.org/doxygen/8.0/qsv_transcode_8c-example

Initializes the FFmpeg decoder context, including setting hardware device context, frame rate, and opening the codec. It handles potential errors during device reference creation and codec opening. Dependencies include FFmpeg libraries.

```c
decoder_ctx->framerate = av_guess_frame_rate(ifmt_ctx, video, NULL);
decoder_ctx->hw_device_ctx = av_buffer_ref(hw_device_ctx);
if (!decoder_ctx->hw_device_ctx) {
fprintf(stderr, "A hardware device reference create failed.");
return AVERROR(ENOMEM);
}
decoder_ctx->get_format = get_format;
decoder_ctx->pkt_timebase = video->time_base;
if ((ret = avcodec_open2(decoder_ctx, decoder, NULL)) < 0)
fprintf(stderr, "Failed to open codec for decoding. Error code: %s\n",
av_err2str(ret));
return ret;
}
```

--------------------------------

### Get GUID from AVIOContext - C

Source: https://ffmpeg.org/doxygen/8.0/riffdec_8c

Retrieves a Globally Unique Identifier (GUID) from an AVIOContext. This function is crucial for parsing RIFF-based file formats that use GUIDs to identify data chunks or types. It takes an AVIOContext and a pointer to an ff_asf_guid structure to store the result.

```c
int ff_get_guid(AVIOContext *_s, ff_asf_guid *_g)
```

--------------------------------

### Perform QSV-accelerated transcoding with FFmpeg

Source: https://ffmpeg.org/doxygen/8.0/qsv_transcode_8c-example

This example demonstrates how to perform QSV-accelerated transcoding using FFmpeg. It shows the basic command structure and how to dynamically change encoder options, such as the GOP size, during the transcoding process. The function takes input and output streams, an initial codec configuration, and optional frame number and new option pairs for dynamic updates.

```bash
qsv_transcode input.mp4 h264_qsv output_h264.mp4 "g 60"
qsv_transcode input.mp4 hevc_qsv output_hevc.mp4 "g 60 async_depth 1" 100 "g 120"
```

--------------------------------

### Getting Codec ID from GUID with ff_codec_guid_get_id

Source: https://ffmpeg.org/doxygen/8.0/riffdec_8c_source

Retrieves the AVCodecID corresponding to a given GUID. This function is useful for identifying codecs based on their unique identifiers, often found in container formats.

```c
enum AVCodecID ff_codec_guid_get_id(const AVCodecGuid *guids, ff_asf_guid guid)

```

--------------------------------

### Get TS Payload Start Pointer (C)

Source: https://ffmpeg.org/doxygen/8.0/mpegtsenc_8c

Retrieves a pointer to the start of the payload section within an MPEG-TS packet. This is useful for directly accessing and manipulating the data portion of the packet.

```c
static uint8_t* get_ts_payload_start(uint8_t *_pkt_)
{
    // Implementation details...
}
```

--------------------------------

### FFmpeg Examples

Source: https://ffmpeg.org/doxygen/8.0/intrax8_8h_source

Provides examples of how to use FFmpeg functionalities.

```APIDOC
## FFmpeg Examples

### Description
This section offers practical examples demonstrating the usage of various FFmpeg components and functionalities. These examples are intended to help developers understand how to integrate and utilize the library effectively.

### Request Example
```json
{
  "example": "No request body for viewing examples"
}
```

### Response
#### Success Response (200)
- **Example Title** (string) - A title describing the example.
- **Description** (string) - A brief explanation of what the example demonstrates.
- **Code Snippet** (string) - The actual code demonstrating the usage.
- **Language** (string) - The programming language of the code snippet.

#### Response Example
```json
{
  "Example Title": "Basic Video Transcoding",
  "Description": "Example of transcoding a video file from one format to another using libavformat and libavcodec.",
  "Code Snippet": "// C code snippet demonstrating basic transcoding\n// ... includes and setup ...\nAVFormatContext *input_ctx, *output_ctx;\n// ... open input and output files ...\n// ... stream mapping and codec setup ...\nAVPacket packet;\nwhile (av_read_frame(input_ctx, &packet) >= 0) {\n    // ... process packet and write to output ...\n    av_packet_unref(&packet);\n}\n// ... cleanup ...",
  "Language": "C"
}
```
```

--------------------------------

### List Supported FFmpeg Sample Formats

Source: https://ffmpeg.org/doxygen/8.0/opt__common_8h

Prints a list of all supported sample formats by the FFmpeg program. It takes an optional context and argument pointer.

```c
int | show_sample_fmts (void *optctx, const char *opt, const char *arg)
| Print a listing containing all the sample formats supported by the program. More...

```

--------------------------------

### FFmpeg Main Function Example (C)

Source: https://ffmpeg.org/doxygen/8.0/tests_2hash_8c

A simple main function demonstrating the entry point for a C program using FFmpeg libraries. It includes standard library headers and FFmpeg's libavutil/hash.h. This serves as a basic structure for FFmpeg-related applications.

```c
#include <stdio.h>
#include <string.h>
#include "libavutil/hash.h"

int main (void)
```

--------------------------------

### Get ASF GUID - FFmpeg C

Source: https://ffmpeg.org/doxygen/8.0/wtvdec_8c_source

Retrieves an ASF GUID from an AVIOContext. This function is part of the riffdec.c module and is crucial for parsing Advanced Systems Format (ASF) files.

```c
int ff_get_guid(AVIOContext *s, ff_asf_guid *g)
{
    // Implementation details for reading an ASF GUID
    return 0; // Placeholder for actual return value
}
```

--------------------------------

### libsrt_setup

Source: https://ffmpeg.org/doxygen/8.0/libsrt_8c

Sets up the SRT context with URI and flags.

```APIDOC
## libsrt_setup()

### Description
Sets up the SRT context with URI and flags.

### Method
(Not specified, likely a static function)

### Endpoint
(Not applicable)

### Parameters
#### Path Parameters
(None)

#### Query Parameters
(None)

#### Request Body
(None)

### Request Example
(Not applicable)

### Response
#### Success Response (200)
(Not specified, likely an integer status code)

#### Response Example
(Not specified)
```

--------------------------------

### Get Codec ID from GUID - FFmpeg RIFF

Source: https://ffmpeg.org/doxygen/8.0/riff_8h_source

Determines the AVCodecID from a given AVCodecGuid. This function is the inverse of `ff_get_codec_guid` and is used during demuxing to identify the codec associated with a GUID found in the stream.

```c
enum AVCodecID ff_codec_guid_get_id(const AVCodecGuid *guids, ff_asf_guid guid)
{
    // ... implementation ...
    return AVCodecID_NONE;
}
```

--------------------------------

### Setup Functions for Various Modules

Source: https://ffmpeg.org/doxygen/8.0/globals_s

A collection of 'setup' functions used across FFmpeg for initializing and configuring various components. These range from setting up convolution filters, audio/video streams, compression parameters, and hardware contexts. They are crucial for the proper functioning of FFmpeg's processing pipelines.

```c
void setup_3x3();
void setup_5x5();
void setup_7x7();
void setup_array(AVAudioResampleContext *ctx);
void setup_bumping(AVCodecContext *avctx);
void setup_classifs(VorbisDecContext *s);
void setup_column();
void setup_compress_thresh(AudioFilterContext *ctx);
void setup_crossbar_options(DshowCrossbar *crossbar);
void setup_derivative_buffers(ColorConstancyContext *ctx);
void setup_find_stream_info_opts(AVFormatContext *s, AVCodecContext *avctx);
void setup_frame(AVCodecContext *avctx);
void setup_legacy_swscale(GraphContext *graph);
void setup_lru_555(DxtoryContext *dxtory);
void setup_lru_565(DxtoryContext *dxtory);
void setup_lut3d(GraphContext *graph);
void setup_mb_info(AVCodecContext *avctx);
void setup_multilayer(HEVCContext *s);
void setup_partitions(VP8Context *s);
void setup_pps(PSContext *s);
void setup_qtables(MobiclipContext *q);
void setup_queue_families(VulkanContext *vulkan);
void setup_refs(AVCodecContext *avctx);
void setup_roi(AVCodecContext *avctx);
void setup_row();
void setup_sce(AACDecUSACContext *s);
void setup_side_data_entry(AVPacket *pkt);
void setup_slices(AVCodecContext *avctx);
void setup_srtp(WhipContext *whip);
void setup_sync_queues(FFmpegMuxContext *muxer);
void setup_window(XcbGrabContext *xcbgrab);

```

--------------------------------

### Get SOT (JPEG2000 Start of Tile) (C)

Source: https://ffmpeg.org/doxygen/8.0/jpeg2000dec_8c_source

Parses and retrieves the Start Of Tile (SOT) marker information from the JPEG2000 bitstream. This function is crucial for identifying tile boundaries during decoding.

```c
static int get_sot(Jpeg2000DecoderContext *s, int n)
jpeg2000dec.c
```

--------------------------------

### av_gettime_relative - Get Relative Time

Source: https://ffmpeg.org/doxygen/8.0/time_8c_source

Gets the current time in microseconds relative to an unspecified starting point. It utilizes `clock_gettime` with `CLOCK_MONOTONIC` on systems that support it, otherwise it falls back to `av_gettime` with an offset.

```APIDOC
## GET /av_gettime_relative

### Description
Get the current time in microseconds since some unspecified starting point.

### Method
GET

### Endpoint
/av_gettime_relative

### Parameters
None

### Request Example
None

### Response
#### Success Response (200)
- **int64_t** - The relative current time in microseconds.

#### Response Example
```json
{
  "relative_time_microseconds": 1678886400123456
}
```
```

--------------------------------

### FFmpeg Configuration Header and Utility Includes

Source: https://ffmpeg.org/doxygen/8.0/riscv_2g722dsp__init_8c_source

This code snippet includes necessary configuration headers and utility files for FFmpeg. It sets up the build environment and provides access to CPU-specific features and attributes, crucial for performance optimizations and hardware acceleration.

```c
#include "config.h"

#include <stdint.h>

#include "libavutil/attributes.h"
#include "libavutil/cpu.h"
#include "libavutil/riscv/cpu.h"
#include "libavcodec/g722dsp.h"

```

--------------------------------

### FFmpeg Configuration and Setup Functions

Source: https://ffmpeg.org/doxygen/8.0/vp9dsp__template_8c

This snippet includes functions for setting up and configuring FFmpeg components, such as context initialization, dimension setting, and default control value configuration.

```c
setctx_2d()
set_dimensions()
set_default_ctl_value()
set_intra_mode_default()
set_mv_intra()
set_tb_tab()
setup_3x3()
setup_5x5()
setup_7x7()
setup_column()
setup_color_transform()
update_canvas_size()
update_input_arguments()
update_model5_to_6()
update_size()
urlcontext_child_next()
urlcontext_to_name()
```

--------------------------------

### Get Codec ID from GUID (C)

Source: https://ffmpeg.org/doxygen/8.0/riff_8h

Determines the FFmpeg AVCodecID from a list of AVCodecGuid structures and a specific ff_asf_guid. This function is used during demuxing to identify the codec associated with a GUID found in the file header.

```c
enum AVCodecID ff_codec_guid_get_id(
    const AVCodecGuid *_guids_,
    ff_asf_guid _guid_
);
```

--------------------------------

### QSV Initialization Functions (C)

Source: https://ffmpeg.org/doxygen/8.0/qsv__internal_8h_source

Provides functions for initializing QSV sessions and devices within FFmpeg. These functions handle the setup of the Quick Sync Video environment, including device and session creation, plugin loading, and GPU copy settings. They are crucial for enabling hardware-accelerated video processing with QSV.

```c
int ff_qsv_init_internal_session(AVCodecContext *avctx, QSVSession *qs, const char *load_plugins, int gpu_copy)

```

```c
int ff_qsv_init_session_frames(AVCodecContext *avctx, mfxSession *session, QSVFramesContext *qsv_frames_ctx, const char *load_plugins, int opaque, int gpu_copy)

```

```c
int ff_qsv_init_session_device(AVCodecContext *avctx, mfxSession *psession, AVBufferRef *device_ref, const char *load_plugins, int gpu_copy)

```

--------------------------------

### MPEG-4 Next Start Code Search (Studio Mode)

Source: https://ffmpeg.org/doxygen/8.0/mpeg4videodec_8c_source

Aligns the get bit context and searches for the next start code in studio mode. This function is essential for segmenting the bitstream into frames or slices.

```c
static void next_start_code_studio(GetBitContext *gb)
{
    align_get_bits(gb);

    while (get_bits_left(gb) >= 24 && show_bits(gb, 24) != 0x1) {
        get_bits(gb, 8);
    }
}

```

--------------------------------

### Get FFmpeg Codec ID from GUID Array

Source: https://ffmpeg.org/doxygen/8.0/riffdec_8c_source

Retrieves an AVCodecID by comparing a given ff_asf_guid against an array of AVCodecGuid structures. It iterates through the provided GUIDs and returns the corresponding ID if a match is found, otherwise returns AV_CODEC_ID_NONE. This is used to map specific GUIDs to FFmpeg's codec identifiers.

```c
enum AVCodecID ff_codec_guid_get_id(const AVCodecGuid *guids, ff_asf_guid guid)
{
    int i;
    for (i = 0; guids[i].id != AV_CODEC_ID_NONE; i++)
        if (!ff_guidcmp(guids[i].guid, guid))
            return guids[i].id;
    return AV_CODEC_ID_NONE;
}
```

--------------------------------

### Initialize VVC Entry Point with WPP (C)

Source: https://ffmpeg.org/doxygen/8.0/thread_8c_source

Initializes a new VVC entry point (`next`) based on an existing one (`ep`) and the sequence parameter set (`sps`). It copies CABAC state and processing parameters, and then calls `ff_vvc_ep_init_stat_coeff` to set up coefficient statistics, essential for Wavefront Parallel Processing (WPP) synchronization.

```c
static void ep_init_wpp(EntryPoint *next, const EntryPoint *ep, const VVCSPS *sps)
{
        memcpy(next->cabac_state, ep->cabac_state, sizeof(next->cabac_state));
        memcpy(next->pp, ep->pp, sizeof(next->pp));
        ff_vvc_ep_init_stat_coeff(next, sps->bit_depth, sps->r->sps_persistent_rice_adaptation_enabled_flag);
}
```

--------------------------------

### FFmpeg Structures for FFASF GUIDs and Data

Source: https://ffmpeg.org/doxygen/8.0/wtvdec_8c_source

Defines constants and structures related to ASF (Advanced Systems Format) GUIDs. These GUIDs are used to identify different media types and data structures within ASF files. Examples include ff_format_waveformatex, ff_stream1_guid, ff_index_guid, ff_data_guid, and mediasubtype_teletext.

```c
typedef struct ff_asf_guid {
  // ...
} ff_asf_guid;

const ff_asf_guid ff_format_waveformatex;
const ff_asf_guid ff_stream1_guid;
const ff_asf_guid ff_index_guid;
const ff_asf_guid ff_data_guid;
static const ff_asf_guid mediasubtype_teletext;

```