### Configure Build Options for dav1d

Source: https://github.com/videolan/dav1d/blob/master/meson_options.txt

This snippet demonstrates how to configure various build options for the dav1d project. These options control which components are built, including tools, examples, tests, and documentation, as well as enabling or disabling specific features like assembly code generation and logging.

```python
option('enable_asm',
    type: 'boolean',
    value: true,
    description: 'Build asm files, if available')

option('enable_tools',
    type: 'boolean',
    value: true,
    description: 'Build dav1d cli tools')

option('enable_examples',
    type: 'boolean',
    value: false,
    description: 'Build dav1d examples')

option('enable_tests',
    type: 'boolean',
    value: true,
    description: 'Build dav1d tests')

option('enable_docs',
    type: 'boolean',
    value: false,
    description: 'Build dav1d documentation')
```

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

### Implement Custom Logger Callback with dav1d

Source: https://context7.com/videolan/dav1d/llms.txt

This example illustrates how to set up a custom logging callback for the dav1d decoder. It defines a log_callback function that writes messages to a specified file and configures the dav1d_settings to use this callback.

```c
#include "dav1d/dav1d.h"
#include <stdio.h>
#include <stdarg.h>

void log_callback(void *cookie, const char *format, va_list args) {
    FILE *log_file = (FILE *)cookie;
    vfprintf(log_file, format, args);
    fprintf(log_file, "\n");
    fflush(log_file);
}

int main(void) {
    FILE *log_file = fopen("decoder.log", "w");
    Dav1dSettings settings;

    dav1d_default_settings(&settings);
    settings.logger.cookie = log_file;
    settings.logger.callback = log_callback;

    Dav1dContext *ctx;
    dav1d_open(&ctx, &settings);

    // Decoder will now log messages to file

    dav1d_close(&ctx);
    fclose(log_file);
    return 0;
}
```

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

### Implement Custom Picture Allocator with dav1d

Source: https://context7.com/videolan/dav1d/llms.txt

This example shows how to implement a custom memory allocator for decoded picture buffers using dav1d. It involves defining allocation and release callback functions and configuring the dav1d_settings with these callbacks.

```c
#include "dav1d/dav1d.h"
#include <stdlib.h>

typedef struct {
    void *pool;
    // Custom allocator state
} MyAllocator;

int alloc_picture_callback(Dav1dPicture *pic, void *cookie) {
    MyAllocator *alloc = (MyAllocator *)cookie;

    // Calculate required buffer sizes with alignment
    size_t y_size = pic->p.h * 128 + DAV1D_PICTURE_ALIGNMENT;
    size_t uv_h = (pic->p.h + 1) >> 1;
    size_t uv_size = uv_h * 128 + DAV1D_PICTURE_ALIGNMENT;

    // Allocate aligned buffers
    pic->data[0] = aligned_alloc(DAV1D_PICTURE_ALIGNMENT, y_size);
    pic->data[1] = aligned_alloc(DAV1D_PICTURE_ALIGNMENT, uv_size);
    pic->data[2] = aligned_alloc(DAV1D_PICTURE_ALIGNMENT, uv_size);

    if (!pic->data[0] || !pic->data[1] || !pic->data[2]) {
        return DAV1D_ERR(ENOMEM);
    }

    pic->stride[0] = 128;  // Y stride (must be multiple of 128)
    pic->stride[1] = 128;  // UV stride (must match for U and V)
    pic->allocator_data = cookie;

    return 0;
}

void release_picture_callback(Dav1dPicture *pic, void *cookie) {
    free(pic->data[0]);
    free(pic->data[1]);
    free(pic->data[2]);
}

// Configure decoder with custom allocator
Dav1dSettings settings;
MyAllocator my_alloc = {0};

dav1d_default_settings(&settings);
settings.allocator.cookie = &my_alloc;
settings.allocator.alloc_picture_callback = alloc_picture_callback;
settings.allocator.release_picture_callback = release_picture_callback;

Dav1dContext *ctx;
dav1d_open(&ctx, &settings);
```

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

### C: Dav1d Complete Decoding Loop Example

Source: https://context7.com/videolan/dav1d/llms.txt

Demonstrates a full decoding loop using dav1d, including reading data from a file, sending it to the decoder, retrieving decoded pictures, and handling errors. It also includes logic for draining any remaining buffered frames after the input is exhausted.

```c
#include "dav1d/dav1d.h"
#include <stdio.h>
#include <errno.h>

int decode_stream(FILE *input, Dav1dContext *ctx) {
    Dav1dData data = {0};
    Dav1dPicture pic = {0};
    int res;

    // Main decoding loop
    while (1) {
        // Read input data
        if (data.sz == 0) {
            uint8_t *buf = dav1d_data_create(&data, 4096);
            if (!buf) break;

            size_t bytes = fread(buf, 1, 4096, input);
            if (bytes == 0) {
                dav1d_data_unref(&data);
                break;  // EOF
            }
            data.sz = bytes;
        }

        // Send data to decoder
        res = dav1d_send_data(ctx, &data);
        if (res < 0 && res != DAV1D_ERR(EAGAIN)) {
            fprintf(stderr, "Send error: %d\n", res);
            dav1d_data_unref(&data);
            return res;
        }

        // Retrieve decoded pictures
        while (1) {
            res = dav1d_get_picture(ctx, &pic);
            if (res == DAV1D_ERR(EAGAIN)) {
                break;  // Need more input data
            } else if (res < 0) {
                fprintf(stderr, "Decode error: %d\n", res);
                return res;
            }

            // Process decoded picture
            printf("Frame %ldx%ld pts=%ld\n",
                   (long)pic.p.w, (long)pic.p.h, (long)pic.m.timestamp);
            dav1d_picture_unref(&pic);
        }
    }

    // Drain buffered frames
    while (1) {
        res = dav1d_get_picture(ctx, &pic);
        if (res == DAV1D_ERR(EAGAIN)) break;
        if (res < 0) return res;

        printf("Drained frame %ldx%ld\n", (long)pic.p.w, (long)pic.p.h);
        dav1d_picture_unref(&pic);
    }

    return 0;
}
```

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

### Get dav1d Library and API Version

Source: https://context7.com/videolan/dav1d/llms.txt

This C code snippet shows how to retrieve the dav1d library version string and the API version number at runtime. It uses dav1d_version() and dav1d_version_api() functions.

```c
#include "dav1d/dav1d.h"
#include <stdio.h>

void print_version_info(void) {
    const char *version = dav1d_version();
    unsigned api_version = dav1d_version_api();

    printf("dav1d version: %s\n", version);
    printf("API version: %d.%d.%d\n",
           (api_version >> 16) & 0xFF,
           (api_version >> 8) & 0xFF,
           api_version & 0xFF);
}
```

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

### Access Picture Metadata and HDR Info with dav1d

Source: https://context7.com/videolan/dav1d/llms.txt

This example demonstrates how to access metadata from decoded pictures using dav1d, including timestamps, duration, offset, and HDR information like content light and mastering display parameters. It also shows how to access frame header details.

```c
#include "dav1d/dav1d.h"

Dav1dPicture pic = {0};

if (dav1d_get_picture(ctx, &pic) == 0) {
    // Access basic metadata
    printf("PTS: %ld\n", (long)pic.m.timestamp);
    printf("Duration: %ld\n", (long)pic.m.duration);
    printf("Offset: %ld\n", (long)pic.m.offset);

    // Access HDR metadata
    if (pic.content_light) {
        printf("Max content light: %d\n", pic.content_light->max_content_light_level);
        printf("Max frame average: %d\n", pic.content_light->max_frame_average_light_level);
    }

    if (pic.mastering_display) {
        printf("Display primaries: R(%d,%d) G(%d,%d) B(%d,%d)\n",
               pic.mastering_display->primaries[0][0],
               pic.mastering_display->primaries[0][1],
               pic.mastering_display->primaries[1][0],
               pic.mastering_display->primaries[1][1],
               pic.mastering_display->primaries[2][0],
               pic.mastering_display->primaries[2][1]);
    }

    // Access frame headers
    if (pic.frame_hdr) {
        printf("Frame type: %d\n", pic.frame_hdr->frame_type);
        printf("Show frame: %d\n", pic.frame_hdr->show_frame);
    }

    dav1d_picture_unref(&pic);
}
```

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

### C: Dav1d Apply Film Grain Example

Source: https://context7.com/videolan/dav1d/llms.txt

Demonstrates how to manually apply film grain synthesis to a decoded picture using dav1d. This requires an input picture obtained with film grain synthesis disabled in the decoder settings. The function generates an output picture with the grain applied and must be unreferenced afterward.

```c
#include "dav1d/dav1d.h"

Dav1dPicture input_pic = {0};
Dav1dPicture output_pic = {0};

// Get picture without film grain applied
// (settings.apply_grain must be 0)
dav1d_get_picture(ctx, &input_pic);

// Apply film grain manually
int res = dav1d_apply_grain(ctx, &output_pic, &input_pic);
if (res == 0) {
    // output_pic now contains picture with film grain applied
    // Use output_pic for display
    dav1d_picture_unref(&output_pic);
} else {
    fprintf(stderr, "Failed to apply grain: %d\n", res);
}

dav1d_picture_unref(&input_pic);
```

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

### C: Dav1d Parse Sequence Header Example

Source: https://context7.com/videolan/dav1d/llms.txt

Parses a sequence header from a given bitstream data without performing full decoding. It extracts key information like resolution, profile, bit depth, chroma subsampling, and film grain presence. Handles cases where no header is found or parsing errors occur.

```c
#include "dav1d/dav1d.h"
#include "dav1d/headers.h"

Dav1dSequenceHeader seq_hdr;
uint8_t *bitstream_data = /* ... */;
size_t bitstream_size = /* ... */;

int res = dav1d_parse_sequence_header(&seq_hdr, bitstream_data, bitstream_size);
if (res == 0) {
    printf("Resolution: %dx%d\n", seq_hdr.max_width, seq_hdr.max_height);
    printf("Profile: %d\n", seq_hdr.profile);
    printf("Bit depth: %d\n", seq_hdr.hbd ? (seq_hdr.hbd == 1 ? 10 : 12) : 8);
    printf("Chroma subsampling: %d\n", seq_hdr.layout);
    printf("Film grain: %d\n", seq_hdr.film_grain_present);
} else if (res == DAV1D_ERR(ENOENT)) {
    fprintf(stderr, "No sequence header found in data\n");
} else {
    fprintf(stderr, "Parse error: %d\n", res);
}
```

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

### Configure Performance and Feature Options for dav1d

Source: https://github.com/videolan/dav1d/blob/master/meson_options.txt

This snippet covers configuration options for performance tuning and feature selection in dav1d. It includes settings for bitdepths, stack alignment, XXH32 muxer behavior, and an option to trim redundant DSP functions based on build type.

```python
option('bitdepths',
    type: 'array',
    choices: ['8', '16'],
    description: 'Enable only specified bitdepths')

option('stack_alignment',
    type: 'integer',
    value: 0)

option('xxhash_muxer',
    type : 'feature',
    value : 'auto')

option('trim_dsp',
    type: 'combo',
    choices: ['true', 'false', 'if-release'],
    value: 'if-release',
    description: 'Eliminate redundant DSP functions where possible')
```

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

### Configure Fuzzing and Testing Options for dav1d

Source: https://github.com/videolan/dav1d/blob/master/meson_options.txt

This snippet details the configuration options related to fuzzing and testing within the dav1d project. It includes choices for fuzzing engines, flags for fuzzer linking, and options to enable specific test scenarios like seek stress and tests requiring additional data.

```python
option('enable_seek_stress',
    type: 'boolean',
    value: false,
    description: 'Build seek_stress test tool')

option('testdata_tests',
    type: 'boolean',
    value: false,
    description: 'Run tests requiring the test data repository')

option('fuzzing_engine',
    type: 'combo',
    choices : ['none', 'libfuzzer', 'oss-fuzz'],
    value: 'none',
    description: 'Select the fuzzing engine')

option('fuzzer_ldflags',
    type: 'string',
    description: 'Extra LDFLAGS used during linking of fuzzing binaries')
```

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

### Configure Logging and macOS Specific Options for dav1d

Source: https://github.com/videolan/dav1d/blob/master/meson_options.txt

This snippet demonstrates how to configure logging behavior and macOS-specific features in dav1d. The logging option controls whether error messages are printed using a callback, and the macos_kperf option enables the use of the private macOS kperf API for benchmarking.

```python
option('logging',
    type: 'boolean',
    value: true,
    description: 'Print error log messages using the provided callback function')

option('macos_kperf',
    type: 'boolean',
    value: false,
    description: 'Use the private macOS kperf API for benchmarking')
```

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

### Open dav1d Decoder Context (C)

Source: https://context7.com/videolan/dav1d/llms.txt

Allocates and initializes a dav1d decoder context using the provided Dav1dSettings. It handles potential errors during context opening and includes cleanup for the context.

```c
#include "dav1d/dav1d.h"
#include <stdio.h>

Dav1dContext *ctx = NULL;
Dav1dSettings settings;

dav1d_default_settings(&settings);
settings.n_threads = 0;  // Auto-detect number of cores

int res = dav1d_open(&ctx, &settings);
if (res < 0) {
    fprintf(stderr, "Failed to open decoder: %d\n", res);
    return -1;
}

// Use decoder...

// Clean up when done
dav1d_close(&ctx);  // ctx will be set to NULL
```

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

### Initialize dav1d Decoder Settings (C)

Source: https://context7.com/videolan/dav1d/llms.txt

Initializes a Dav1dSettings structure with default values and configures various decoder parameters such as threading, frame delay, film grain application, operating point selection, layer output, and filter/frame type decoding.

```c
#include "dav1d/dav1d.h"

Dav1dSettings settings;
dav1d_default_settings(&settings);

// Configure threading
settings.n_threads = 4;  // Use 4 threads (0 = auto-detect cores)
settings.max_frame_delay = 1;  // Low latency mode

// Configure decoding behavior
settings.apply_grain = 1;  // Apply film grain (default)
settings.operating_point = 0;  // Select operating point for scalable streams
settings.all_layers = 1;  // Output all spatial layers

// Configure filtering
settings.inloop_filters = DAV1D_INLOOPFILTER_ALL;  // Enable all filters
settings.decode_frame_type = DAV1D_DECODEFRAMETYPE_ALL;  // Decode all frames
```

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

### Allocate Input Data Buffer for dav1d (C)

Source: https://context7.com/videolan/dav1d/llms.txt

Creates a buffer to hold encoded AV1 bitstream data for the dav1d decoder. It allocates memory, reads data into the buffer, optionally sets metadata like timestamp and duration, and sends the data to the decoder.

```c
#include "dav1d/dav1d.h"
#include <stdio.h>
#include <string.h>

Dav1dData data = {0};
size_t buffer_size = 4096;

uint8_t *buf = dav1d_data_create(&data, buffer_size);
if (!buf) {
    fprintf(stderr, "Failed to allocate data buffer\n");
    return -1;
}

// Read encoded data into buffer
size_t bytes_read = fread(buf, 1, buffer_size, input_file);
data.sz = bytes_read;

// Optional: Set metadata
data.m.timestamp = frame_timestamp;
data.m.duration = frame_duration;
data.m.offset = stream_offset;

// Send to decoder (ownership transfers on success)
int res = dav1d_send_data(ctx, &data);
if (res < 0) {
    dav1d_data_unref(&data);  // Clean up on error
}
```

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

### Check Decoder Events with dav1d

Source: https://context7.com/videolan/dav1d/llms.txt

This snippet demonstrates how to check for various decoder events, such as new sequence headers or parameter changes, using dav1d_get_event_flags. It requires a valid Dav1dContext and a Dav1dPicture.

```c
#include "dav1d/dav1d.h"

Dav1dPicture pic = {0};
enum Dav1dEventFlags flags;

if (dav1d_get_picture(ctx, &pic) == 0) {
    // Check for events
    if (dav1d_get_event_flags(ctx, &flags) == 0) {
        if (flags & DAV1D_EVENT_FLAG_NEW_SEQUENCE) {
            printf("New coded sequence started\n");
            // Handle resolution change, format change, etc.
        }
        if (flags & DAV1D_EVENT_FLAG_NEW_OP_PARAMS_INFO) {
            printf("Operating parameters changed\n");
        }
    }

    dav1d_picture_unref(&pic);
}
```

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

### Wrap External Data Buffer for dav1d (C)

Source: https://context7.com/videolan/dav1d/llms.txt

Wraps an existing memory buffer for use with the dav1d decoder without copying data. It requires a callback function for memory cleanup and associates it with the Dav1dData structure.

```c
#include "dav1d/dav1d.h"
#include <stdlib.h>

void free_callback(const uint8_t *buf, void *cookie) {
    free((void *)buf);
}

Dav1dData data = {0};
uint8_t *external_buffer = malloc(size);
// ... fill buffer with data ...

int res = dav1d_data_wrap(&data, external_buffer, size,
                          free_callback, NULL);
if (res < 0) {
    free(external_buffer);
    fprintf(stderr, "Failed to wrap data: %d\n", res);
    return -1;
}

data.m.timestamp = pts;
dav1d_send_data(ctx, &data);
```

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

### C: Flush Dav1d Decoder State

Source: https://context7.com/videolan/dav1d/llms.txt

Illustrates how to flush the internal state and buffered frames of the dav1d decoder. This operation is typically used when seeking within the media stream to ensure that decoding restarts correctly from the new position after a valid sequence header.

```c
#include "dav1d/dav1d.h"

void seek_to_position(Dav1dContext *ctx, FILE *file, long position) {
    // Flush decoder before seeking
    dav1d_flush(ctx);

    // Seek to new position
    fseek(file, position, SEEK_SET);

    // Continue decoding from new position
    // Note: Decoding starts after valid sequence header OBU
}
```

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

### Send Data to dav1d Decoder (C)

Source: https://context7.com/videolan/dav1d/llms.txt

Feeds encoded AV1 bitstream data to the dav1d decoder. It handles potential errors such as the decoder buffer being full (EAGAIN) or other transmission failures, and manages data ownership transfer.

```c
#include "dav1d/dav1d.h"
#include <errno.h>

Dav1dData data = {0};
uint8_t *buf = dav1d_data_create(&data, 8192);
size_t bytes = fread(buf, 1, 8192, file);
data.sz = bytes;

int res = dav1d_send_data(ctx, &data);
if (res == DAV1D_ERR(EAGAIN)) {
    // Decoder buffer full - retrieve pictures first
    fprintf(stderr, "Decoder busy, get pictures before sending more data\n");
    // data still owned by caller, can retry
} else if (res < 0) {
    // Other error occurred
    fprintf(stderr, "Send data failed: %d\n", res);
    dav1d_data_unref(&data);
} else {
    // Success - ownership transferred to decoder
    // Do not call dav1d_data_unref()
}
```

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

### C: Retrieve Decoded Picture from Dav1d

Source: https://context7.com/videolan/dav1d/llms.txt

Retrieves a decoded frame from the dav1d decoder's output queue. It checks for success, prints frame details, allows access to pixel data, and requires explicit unreferencing of the picture when done. Handles cases where no picture is immediately available.

```c
#include "dav1d/dav1d.h"

Dav1dPicture pic = {0};

int res = dav1d_get_picture(ctx, &pic);
if (res == 0) {
    // Picture successfully retrieved
    printf("Decoded frame: %dx%d, stride=%td, bpc=%d\n",
           pic.p.w, pic.p.h, pic.stride[0], pic.p.bpc);

    // Access picture data
    uint8_t *y_plane = pic.data[0];
    uint8_t *u_plane = pic.data[1];
    uint8_t *v_plane = pic.data[2];

    // Process picture data...

    // Must unref when done
    dav1d_picture_unref(&pic);
} else if (res == DAV1D_ERR(EAGAIN)) {
    // No picture available, send more data
} else {
    fprintf(stderr, "Get picture failed: %d\n", res);
}
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.