[FFmpeg-devel] examples/vaapi_dec: Add a VA-API hwaccel decoding example

From 6b56c541ed7dd271ad0aa6eb6412a8427f009525 Mon Sep 17 00:00:00 2001
From: Jun Zhao <jun.zhao@intel.com>
Date: Tue, 21 Mar 2017 11:04:41 +0800
Subject: [PATCH] examples/vaapi_dec: Add a VA-API hwaccel decoding example.

Add a VA-API hwaccel decoding example.

Signed-off-by: Liu, Kaixuan <kaixuan.liu@intel.com>
Signed-off-by: Jun Zhao <jun.zhao@intel.com>
---
 doc/examples/vaapi_dec.c | 346 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 346 insertions(+)
 create mode 100644 doc/examples/vaapi_dec.c

On Tue, 21 Mar 2017 12:45:26 +0800
Jun Zhao <mypopydev@gmail.com> wrote:

> From 6b56c541ed7dd271ad0aa6eb6412a8427f009525 Mon Sep 17 00:00:00 2001
> From: Jun Zhao <jun.zhao@intel.com>
> Date: Tue, 21 Mar 2017 11:04:41 +0800
> Subject: [PATCH] examples/vaapi_dec: Add a VA-API hwaccel decoding example.
> 
> Add a VA-API hwaccel decoding example.
> 
> Signed-off-by: Liu, Kaixuan <kaixuan.liu@intel.com>
> Signed-off-by: Jun Zhao <jun.zhao@intel.com>
> ---
>  doc/examples/vaapi_dec.c | 346 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 346 insertions(+)
>  create mode 100644 doc/examples/vaapi_dec.c
> 
> diff --git a/doc/examples/vaapi_dec.c b/doc/examples/vaapi_dec.c
> new file mode 100644
> index 0000000..f975d86
> --- /dev/null
> +++ b/doc/examples/vaapi_dec.c
> @@ -0,0 +1,346 @@
> +/*
> + * Video Acceleration API (video decoding) decode sample
> + *
> + * 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
> + */
> +
> +/**
> + * @file
> + * Intel VAAPI-accelerated decoding example.
> + *
> + * @example vaapi_dec.c
> + * This example shows how to do VAAPI-accelerated decoding with output
> + * frames from the VAAPI video surfaces.
> + */
> +
> +#include <stdio.h>
> +#include <libavcodec/avcodec.h>
> +#include <libavcodec/vaapi.h>
> +#include <libavformat/avformat.h>
> +#include <libswscale/swscale.h>
> +#include <libavutil/pixdesc.h>
> +#include <libavutil/hwcontext.h>
> +#include <libavutil/opt.h>
> +#include <libavutil/hwcontext_vaapi.h>
> +#include <libavutil/avassert.h>
> +#include <va/va.h>
> +#include <va/va_x11.h>
> +#include <va/va_drm.h>
> +
> +#define DEFAULT_SURFACES 20
> +static enum AVPixelFormat decode_format = AV_PIX_FMT_NV12;
> +static enum AVPixelFormat output_format = AV_PIX_FMT_NV12; /* default output format nv12 */
> +static AVBufferRef *frames_ref = NULL;
> +static AVBufferRef *device_ref = NULL;
> +FILE *output_file = NULL;
> +
> +void decoder_uninit_vaapi(AVCodecContext *avctx, AVVAAPIDeviceContext *hwctx)
> +{
> +    if (hwctx) {
> +        av_buffer_unref(&frames_ref);
> +        av_buffer_unref(&device_ref);
> +    }
> +    return;
> +}
> +
> +int decoder_init_vaapi(AVCodecContext *ctx)
> +{
> +    AVBufferRef *hw_device_ctx = NULL;
> +    AVHWFramesContext *frames;
> +    int err = 0;
> +    char *dev_name = "/dev/dri/renderD128";
> +    AVBufferRef *device_ref = NULL;
> +    AVHWDeviceContext *device = NULL;
> +    AVVAAPIDeviceContext *hwctx = NULL;
> +
> +    if ((err = av_hwdevice_ctx_create(&hw_device_ctx, AV_HWDEVICE_TYPE_VAAPI,
> +                                      dev_name, NULL, 0)) < 0) {
> +        fprintf(stderr, "Failed to create a VAAPI device.\n");
> +        return err;
> +    }
> +
> +    device_ref = av_buffer_ref(hw_device_ctx);
> +    device = (AVHWDeviceContext *)device_ref->data;
> +    hwctx = (AVVAAPIDeviceContext *)device->hwctx;
> +
> +    ctx->pix_fmt = output_format;
> +    if (!(frames_ref = av_hwframe_ctx_alloc(device_ref))) {
> +        fprintf(stderr, "Failed to create VAAPI frame context.\n");
> +        err = AVERROR(ENOMEM);
> +        goto fail;
> +    }
> +    frames = (AVHWFramesContext *)frames_ref->data;
> +    frames->format    = AV_PIX_FMT_VAAPI;
> +    frames->sw_format = decode_format;
> +    frames->width     = ctx->coded_width;
> +    frames->height    = ctx->coded_height;
> +    frames->initial_pool_size = DEFAULT_SURFACES;
> +    if ((err = av_hwframe_ctx_init(frames_ref)) < 0) {
> +        fprintf(stderr, "Failed to initialize VAAPI frame.\n");
> +        goto fail;
> +    }
> +
> +    ctx->hw_frames_ctx = av_buffer_ref(frames_ref);
> +    if (!ctx->hw_frames_ctx) {
> +        err = AVERROR(ENOMEM);
> +        fprintf(stderr, "Failed to ref VAAPI frame.\n");
> +        goto fail;
> +    }

All of this code (except device creation) will be unnecessary once the
Libav change of improving the hw decoding API has been merged. See e.g.:

https://git.libav.org/?p=libav.git;a=commit;h=62a1ef9f26c654a3e988aa465c4ac1d776c4c356

> +
> +fail:
> +    if (err < 0)
> +        decoder_uninit_vaapi(ctx, hwctx);
> +    return err;
> +}
> +
> +static enum AVPixelFormat get_hw_vaapi_format(AVCodecContext *ctx,
> +                                              const enum AVPixelFormat *pix_fmts)
> +{
> +    const enum AVPixelFormat *p;
> +    int ret;
> +
> +    for (p = pix_fmts; *p != -1; p++) {
> +        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
> +        if (!(desc->flags & AV_PIX_FMT_FLAG_HWACCEL))
> +            break;
> +
> +        if (!(strstr(desc->name, "vaapi")))
> +            continue;
> +
> +        if ((ret = decoder_init_vaapi(ctx)) < 0) {
> +            fprintf(stderr, "hwaccel for decoder(VAAPI) cannot be initialized.\n");
> +            return AV_PIX_FMT_NONE;
> +        }
> +        break;
> +    }
> +    return *p;
> +}
> +
> +static int get_hw_vaapi_buffer(AVCodecContext *ctx, AVFrame *frame, int flags)
> +{
> +    int err;
> +    if ((err = av_hwframe_get_buffer(frames_ref, frame, 0)) < 0)
> +        av_log(NULL, AV_LOG_ERROR, "Failed to allocate decoder surface.\n");
> +
> +    return err;
> +}

This function will also be unnecessary.

> +
> +int retrieve_data(AVFrame *input)
> +{
> +    AVFrame *output = 0;
> +    int err;
> +    av_assert0(input->format == AV_PIX_FMT_VAAPI);
> +
> +    if (output_format == AV_PIX_FMT_VAAPI)
> +        return 0;

Not necessary to check the pixfmt. As long as the AVFrame has a
hw_frames_ctx set, it should work. (Even if not, the transfer data
function would just return AVERROR(ENOSYS).)

> +
> +    if (!(output = av_frame_alloc()))
> +        return AVERROR(ENOMEM);
> +    output->format = output_format;
> +    if ((err = av_hwframe_transfer_data(output, input, 0)) < 0) {
> +        fprintf(stderr, "Failed to transfer data to output frame: %d.\n", err);
> +        goto fail;
> +    }
> +
> +    if ((err = av_frame_copy_props(output, input)) < 0) {
> +        av_frame_unref(output);
> +        goto fail;
> +    }
> +
> +    av_frame_unref(input);
> +    av_frame_move_ref(input, output);
> +    av_frame_free(&output);
> +    return 0;
> +
> +fail:
> +    av_frame_free(&output);
> +    return err;
> +}
> +
> +int write_frame(AVFrame *frame)
> +{
> +    int idx, size;
> +    int width = frame->width;
> +    int height = frame->height;
> +
> +    av_assert0(frame && frame->data[0] && output_file);
> +
> +    for (idx = 0; idx < height; idx++) {
> +        if ((size = fwrite(frame->data[0] + idx*frame->linesize[0],
> +                           1, width, output_file)) < 0) {
> +                fprintf(stderr, "Dump Y to file error.\n");
> +                return -1;
> +        }
> +    }
> +
> +    height >>= 1;
> +    for (idx = 0; idx < height; idx++) {
> +        if ((size = fwrite(frame->data[1] + idx*frame->linesize[1],
> +                           1, width, output_file)) < 0) {
> +            fprintf(stderr, "Dump UV to file error.\n");
> +            return -1;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +int decode_write(AVCodecContext *avctx, AVPacket packet, int flush)
> +{
> +    AVFrame *frame = NULL;
> +    int ret = 0, got_frame = 0;
> +
> +    if (!(frame = av_frame_alloc()))
> +        return AVERROR(ENOMEM);
> +
> +    if ((ret = avcodec_decode_video2(avctx, frame, &got_frame, &packet)) < 0) {
> +        fprintf(stderr, "Error during decoding\n");
> +        goto fail;
> +    }

Deprecated API use.

> +
> +    if (got_frame) {
> +        if (AV_PIX_FMT_VAAPI == frame->format) {

I think we want to avoid "yoda conditions" in this project.

> +            /* retrieve data from GPU to CPU */
> +            if ((ret = retrieve_data(frame)) < 0)
> +                goto fail;
> +
> +            if ((ret = write_frame(frame)) < 0)
> +                goto fail;
> +        }
> +    } else if (flush == 1) {
> +            ret = -1;
> +    }
> +
> +fail:
> +    av_frame_free(&frame);
> +    return ret;
> +}
> +
> +/* flush the decoder */
> +int flush(AVCodecContext *avctx)
> +{
> +    AVPacket packet;
> +    int ret = 0;
> +
> +    av_init_packet(&packet);
> +    packet.data = NULL;
> +    packet.size = 0;
> +
> +    while (1) {
> +        if ((ret = decode_write(avctx, packet, 1)) < 0)
> +            break;
> +    }
> +    av_packet_unref(&packet);
> +
> +    return 0;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +    AVFormatContext *input_ctx = NULL;
> +    int i,video_stream,ret;
> +    AVCodecContext *decoder_ctx = NULL;
> +    AVCodec *decoder = NULL;
> +    AVPacket packet;
> +
> +    if (argc < 3) {
> +        fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
> +        return -1;
> +    }
> +
> +    av_register_all();
> +
> +    /* open the input file */
> +    if (avformat_open_input(&input_ctx, argv[1], NULL, NULL) != 0) {
> +        fprintf(stderr, "Cannot open input file '%s'\n", argv[1]);
> +        return -1;
> +    }
> +
> +    if (avformat_find_stream_info(input_ctx, NULL) < 0) {
> +        fprintf(stderr, "Couldn't find input stream information.\n");
> +        return -1;
> +    }
> +
> +    /* find the video stream information */
> +    video_stream = -1;
> +    for (i = 0; i < input_ctx->nb_streams; i++) {
> +        AVStream *st = input_ctx->streams[i];
> +        if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
> +            /* NOTE: just handle the first video stream */
> +            video_stream = i;
> +            break;
> +        }
> +    }
> +
> +    if (video_stream == -1) {
> +        fprintf(stderr, "No find a video stream in the input file.\n");
> +        return -1;
> +    }
> +
> +    /* initialize the video decoder */
> +    if (!(decoder = avcodec_find_decoder(input_ctx->streams[video_stream]->codecpar->codec_id))) {
> +        fprintf(stderr, "Could not find input codec\n");
> +        avformat_close_input(&input_ctx);
> +        return -1;
> +    }
> +
> +    if (!(decoder_ctx = avcodec_alloc_context3(decoder)))
> +        return AVERROR(ENOMEM);
> +
> +    if (avcodec_parameters_to_context(decoder_ctx,
> +                                      input_ctx->streams[video_stream]->codecpar) < 0) {
> +        avcodec_free_context(&decoder_ctx);
> +        avformat_close_input(&input_ctx);
> +        return -1;
> +    }
> +
> +    decoder_ctx->get_format  = get_hw_vaapi_format;
> +    decoder_ctx->get_buffer2 = get_hw_vaapi_buffer;
> +    av_opt_set_int(decoder_ctx, "refcounted_frames", 1, 0);
> +
> +    if ((ret = avcodec_open2(decoder_ctx, decoder, NULL)) < 0) {
> +        fprintf(stderr, "Failed to open codec for stream #%u\n", i);
> +        return ret;
> +    }
> +
> +    /* open the output file to dump YUV */
> +    output_file = fopen(argv[2], "w+");
> +
> +    /* actual decoding and dump the YUV data */
> +    while (av_read_frame(input_ctx, &packet) >= 0) {
> +        if (video_stream == packet.stream_index)
> +                ret = decode_write(decoder_ctx, packet, 0);
> +        av_packet_unref(&packet);
> +
> +        if (ret < 0)
> +                break;
> +    }
> +
> +    /* flush the decoder */
> +    flush(decoder_ctx);
> +
> +    if (output_file)
> +        fclose(output_file);
> +    avcodec_free_context(&decoder_ctx);
> +    avformat_close_input(&input_ctx);
> +
> +    av_buffer_unref(&frames_ref);
> +    av_buffer_unref(&device_ref);
> +
> +    return ret;
> +}
> +

Rest seems ok.

On 2017/3/21 12:57, wm4 wrote:
> On Tue, 21 Mar 2017 12:45:26 +0800
> Jun Zhao <mypopydev@gmail.com> wrote:
> 
>> From 6b56c541ed7dd271ad0aa6eb6412a8427f009525 Mon Sep 17 00:00:00 2001
>> From: Jun Zhao <jun.zhao@intel.com>
>> Date: Tue, 21 Mar 2017 11:04:41 +0800
>> Subject: [PATCH] examples/vaapi_dec: Add a VA-API hwaccel decoding example.
>>
>> Add a VA-API hwaccel decoding example.
>>
>> Signed-off-by: Liu, Kaixuan <kaixuan.liu@intel.com>
>> Signed-off-by: Jun Zhao <jun.zhao@intel.com>
>> ---
>>  doc/examples/vaapi_dec.c | 346 +++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 346 insertions(+)
>>  create mode 100644 doc/examples/vaapi_dec.c
>>
>> diff --git a/doc/examples/vaapi_dec.c b/doc/examples/vaapi_dec.c
>> new file mode 100644
>> index 0000000..f975d86
>> --- /dev/null
>> +++ b/doc/examples/vaapi_dec.c
>> @@ -0,0 +1,346 @@
>> +/*
>> + * Video Acceleration API (video decoding) decode sample
>> + *
>> + * 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
>> + */
>> +
>> +/**
>> + * @file
>> + * Intel VAAPI-accelerated decoding example.
>> + *
>> + * @example vaapi_dec.c
>> + * This example shows how to do VAAPI-accelerated decoding with output
>> + * frames from the VAAPI video surfaces.
>> + */
>> +
>> +#include <stdio.h>
>> +#include <libavcodec/avcodec.h>
>> +#include <libavcodec/vaapi.h>
>> +#include <libavformat/avformat.h>
>> +#include <libswscale/swscale.h>
>> +#include <libavutil/pixdesc.h>
>> +#include <libavutil/hwcontext.h>
>> +#include <libavutil/opt.h>
>> +#include <libavutil/hwcontext_vaapi.h>
>> +#include <libavutil/avassert.h>
>> +#include <va/va.h>
>> +#include <va/va_x11.h>
>> +#include <va/va_drm.h>
>> +
>> +#define DEFAULT_SURFACES 20
>> +static enum AVPixelFormat decode_format = AV_PIX_FMT_NV12;
>> +static enum AVPixelFormat output_format = AV_PIX_FMT_NV12; /* default output format nv12 */
>> +static AVBufferRef *frames_ref = NULL;
>> +static AVBufferRef *device_ref = NULL;
>> +FILE *output_file = NULL;
>> +
>> +void decoder_uninit_vaapi(AVCodecContext *avctx, AVVAAPIDeviceContext *hwctx)
>> +{
>> +    if (hwctx) {
>> +        av_buffer_unref(&frames_ref);
>> +        av_buffer_unref(&device_ref);
>> +    }
>> +    return;
>> +}
>> +
>> +int decoder_init_vaapi(AVCodecContext *ctx)
>> +{
>> +    AVBufferRef *hw_device_ctx = NULL;
>> +    AVHWFramesContext *frames;
>> +    int err = 0;
>> +    char *dev_name = "/dev/dri/renderD128";
>> +    AVBufferRef *device_ref = NULL;
>> +    AVHWDeviceContext *device = NULL;
>> +    AVVAAPIDeviceContext *hwctx = NULL;
>> +
>> +    if ((err = av_hwdevice_ctx_create(&hw_device_ctx, AV_HWDEVICE_TYPE_VAAPI,
>> +                                      dev_name, NULL, 0)) < 0) {
>> +        fprintf(stderr, "Failed to create a VAAPI device.\n");
>> +        return err;
>> +    }
>> +
>> +    device_ref = av_buffer_ref(hw_device_ctx);
>> +    device = (AVHWDeviceContext *)device_ref->data;
>> +    hwctx = (AVVAAPIDeviceContext *)device->hwctx;
>> +
>> +    ctx->pix_fmt = output_format;
>> +    if (!(frames_ref = av_hwframe_ctx_alloc(device_ref))) {
>> +        fprintf(stderr, "Failed to create VAAPI frame context.\n");
>> +        err = AVERROR(ENOMEM);
>> +        goto fail;
>> +    }
>> +    frames = (AVHWFramesContext *)frames_ref->data;
>> +    frames->format    = AV_PIX_FMT_VAAPI;
>> +    frames->sw_format = decode_format;
>> +    frames->width     = ctx->coded_width;
>> +    frames->height    = ctx->coded_height;
>> +    frames->initial_pool_size = DEFAULT_SURFACES;
>> +    if ((err = av_hwframe_ctx_init(frames_ref)) < 0) {
>> +        fprintf(stderr, "Failed to initialize VAAPI frame.\n");
>> +        goto fail;
>> +    }
>> +
>> +    ctx->hw_frames_ctx = av_buffer_ref(frames_ref);
>> +    if (!ctx->hw_frames_ctx) {
>> +        err = AVERROR(ENOMEM);
>> +        fprintf(stderr, "Failed to ref VAAPI frame.\n");
>> +        goto fail;
>> +    }
> 
> All of this code (except device creation) will be unnecessary once the
> Libav change of improving the hw decoding API has been merged. See e.g.:
> 
> https://git.libav.org/?p=libav.git;a=commit;h=62a1ef9f26c654a3e988aa465c4ac1d776c4c356
> 

I like this change, hope it can be move to FFmpeg as quick. Then I will rework this part.

>> +
>> +fail:
>> +    if (err < 0)
>> +        decoder_uninit_vaapi(ctx, hwctx);
>> +    return err;
>> +}
>> +
>> +static enum AVPixelFormat get_hw_vaapi_format(AVCodecContext *ctx,
>> +                                              const enum AVPixelFormat *pix_fmts)
>> +{
>> +    const enum AVPixelFormat *p;
>> +    int ret;
>> +
>> +    for (p = pix_fmts; *p != -1; p++) {
>> +        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
>> +        if (!(desc->flags & AV_PIX_FMT_FLAG_HWACCEL))
>> +            break;
>> +
>> +        if (!(strstr(desc->name, "vaapi")))
>> +            continue;
>> +
>> +        if ((ret = decoder_init_vaapi(ctx)) < 0) {
>> +            fprintf(stderr, "hwaccel for decoder(VAAPI) cannot be initialized.\n");
>> +            return AV_PIX_FMT_NONE;
>> +        }
>> +        break;
>> +    }
>> +    return *p;
>> +}
>> +
>> +static int get_hw_vaapi_buffer(AVCodecContext *ctx, AVFrame *frame, int flags)
>> +{
>> +    int err;
>> +    if ((err = av_hwframe_get_buffer(frames_ref, frame, 0)) < 0)
>> +        av_log(NULL, AV_LOG_ERROR, "Failed to allocate decoder surface.\n");
>> +
>> +    return err;
>> +}
> 
> This function will also be unnecessary.
> 
>> +
>> +int retrieve_data(AVFrame *input)
>> +{
>> +    AVFrame *output = 0;
>> +    int err;
>> +    av_assert0(input->format == AV_PIX_FMT_VAAPI);
>> +
>> +    if (output_format == AV_PIX_FMT_VAAPI)
>> +        return 0;
> 
> Not necessary to check the pixfmt. As long as the AVFrame has a
> hw_frames_ctx set, it should work. (Even if not, the transfer data
> function would just return AVERROR(ENOSYS).)

Agree

> 
>> +
>> +    if (!(output = av_frame_alloc()))
>> +        return AVERROR(ENOMEM);
>> +    output->format = output_format;
>> +    if ((err = av_hwframe_transfer_data(output, input, 0)) < 0) {
>> +        fprintf(stderr, "Failed to transfer data to output frame: %d.\n", err);
>> +        goto fail;
>> +    }
>> +
>> +    if ((err = av_frame_copy_props(output, input)) < 0) {
>> +        av_frame_unref(output);
>> +        goto fail;
>> +    }
>> +
>> +    av_frame_unref(input);
>> +    av_frame_move_ref(input, output);
>> +    av_frame_free(&output);
>> +    return 0;
>> +
>> +fail:
>> +    av_frame_free(&output);
>> +    return err;
>> +}
>> +
>> +int write_frame(AVFrame *frame)
>> +{
>> +    int idx, size;
>> +    int width = frame->width;
>> +    int height = frame->height;
>> +
>> +    av_assert0(frame && frame->data[0] && output_file);
>> +
>> +    for (idx = 0; idx < height; idx++) {
>> +        if ((size = fwrite(frame->data[0] + idx*frame->linesize[0],
>> +                           1, width, output_file)) < 0) {
>> +                fprintf(stderr, "Dump Y to file error.\n");
>> +                return -1;
>> +        }
>> +    }
>> +
>> +    height >>= 1;
>> +    for (idx = 0; idx < height; idx++) {
>> +        if ((size = fwrite(frame->data[1] + idx*frame->linesize[1],
>> +                           1, width, output_file)) < 0) {
>> +            fprintf(stderr, "Dump UV to file error.\n");
>> +            return -1;
>> +        }
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +int decode_write(AVCodecContext *avctx, AVPacket packet, int flush)
>> +{
>> +    AVFrame *frame = NULL;
>> +    int ret = 0, got_frame = 0;
>> +
>> +    if (!(frame = av_frame_alloc()))
>> +        return AVERROR(ENOMEM);
>> +
>> +    if ((ret = avcodec_decode_video2(avctx, frame, &got_frame, &packet)) < 0) {
>> +        fprintf(stderr, "Error during decoding\n");
>> +        goto fail;
>> +    }
> 
> Deprecated API use.
Will rework with send/receive decoding API.
> 
>> +
>> +    if (got_frame) {
>> +        if (AV_PIX_FMT_VAAPI == frame->format) {
> 
> I think we want to avoid "yoda conditions" in this project.
> 
>> +            /* retrieve data from GPU to CPU */
>> +            if ((ret = retrieve_data(frame)) < 0)
>> +                goto fail;
>> +
>> +            if ((ret = write_frame(frame)) < 0)
>> +                goto fail;
>> +        }
>> +    } else if (flush == 1) {
>> +            ret = -1;
>> +    }
>> +
>> +fail:
>> +    av_frame_free(&frame);
>> +    return ret;
>> +}
>> +
>> +/* flush the decoder */
>> +int flush(AVCodecContext *avctx)
>> +{
>> +    AVPacket packet;
>> +    int ret = 0;
>> +
>> +    av_init_packet(&packet);
>> +    packet.data = NULL;
>> +    packet.size = 0;
>> +
>> +    while (1) {
>> +        if ((ret = decode_write(avctx, packet, 1)) < 0)
>> +            break;
>> +    }
>> +    av_packet_unref(&packet);
>> +
>> +    return 0;
>> +}
>> +
>> +int main(int argc, char *argv[])
>> +{
>> +    AVFormatContext *input_ctx = NULL;
>> +    int i,video_stream,ret;
>> +    AVCodecContext *decoder_ctx = NULL;
>> +    AVCodec *decoder = NULL;
>> +    AVPacket packet;
>> +
>> +    if (argc < 3) {
>> +        fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
>> +        return -1;
>> +    }
>> +
>> +    av_register_all();
>> +
>> +    /* open the input file */
>> +    if (avformat_open_input(&input_ctx, argv[1], NULL, NULL) != 0) {
>> +        fprintf(stderr, "Cannot open input file '%s'\n", argv[1]);
>> +        return -1;
>> +    }
>> +
>> +    if (avformat_find_stream_info(input_ctx, NULL) < 0) {
>> +        fprintf(stderr, "Couldn't find input stream information.\n");
>> +        return -1;
>> +    }
>> +
>> +    /* find the video stream information */
>> +    video_stream = -1;
>> +    for (i = 0; i < input_ctx->nb_streams; i++) {
>> +        AVStream *st = input_ctx->streams[i];
>> +        if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
>> +            /* NOTE: just handle the first video stream */
>> +            video_stream = i;
>> +            break;
>> +        }
>> +    }
>> +
>> +    if (video_stream == -1) {
>> +        fprintf(stderr, "No find a video stream in the input file.\n");
>> +        return -1;
>> +    }
>> +
>> +    /* initialize the video decoder */
>> +    if (!(decoder = avcodec_find_decoder(input_ctx->streams[video_stream]->codecpar->codec_id))) {
>> +        fprintf(stderr, "Could not find input codec\n");
>> +        avformat_close_input(&input_ctx);
>> +        return -1;
>> +    }
>> +
>> +    if (!(decoder_ctx = avcodec_alloc_context3(decoder)))
>> +        return AVERROR(ENOMEM);
>> +
>> +    if (avcodec_parameters_to_context(decoder_ctx,
>> +                                      input_ctx->streams[video_stream]->codecpar) < 0) {
>> +        avcodec_free_context(&decoder_ctx);
>> +        avformat_close_input(&input_ctx);
>> +        return -1;
>> +    }
>> +
>> +    decoder_ctx->get_format  = get_hw_vaapi_format;
>> +    decoder_ctx->get_buffer2 = get_hw_vaapi_buffer;
>> +    av_opt_set_int(decoder_ctx, "refcounted_frames", 1, 0);
>> +
>> +    if ((ret = avcodec_open2(decoder_ctx, decoder, NULL)) < 0) {
>> +        fprintf(stderr, "Failed to open codec for stream #%u\n", i);
>> +        return ret;
>> +    }
>> +
>> +    /* open the output file to dump YUV */
>> +    output_file = fopen(argv[2], "w+");
>> +
>> +    /* actual decoding and dump the YUV data */
>> +    while (av_read_frame(input_ctx, &packet) >= 0) {
>> +        if (video_stream == packet.stream_index)
>> +                ret = decode_write(decoder_ctx, packet, 0);
>> +        av_packet_unref(&packet);
>> +
>> +        if (ret < 0)
>> +                break;
>> +    }
>> +
>> +    /* flush the decoder */
>> +    flush(decoder_ctx);
>> +
>> +    if (output_file)
>> +        fclose(output_file);
>> +    avcodec_free_context(&decoder_ctx);
>> +    avformat_close_input(&input_ctx);
>> +
>> +    av_buffer_unref(&frames_ref);
>> +    av_buffer_unref(&device_ref);
>> +
>> +    return ret;
>> +}
>> +
> 
> Rest seems ok.
> 
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