[FFmpeg-devel] [PATCH V2] examples/vaapi_dec: Add a VA-API hwaccel decoding example

Jun Zhao mypopydev at gmail.com
Mon Jul 17 05:51:36 EEST 2017



On 2017/7/11 15:58, wm4 wrote:
> On Tue, 11 Jul 2017 12:06:10 +0800
> Jun Zhao <mypopydev at gmail.com> wrote:
> 
>> From 0e4d230ae4c98949a962c6bbdad31d216b54bb6a Mon Sep 17 00:00:00 2001
>> From: Jun Zhao <jun.zhao at intel.com>
>> Date: Tue, 21 Mar 2017 11:04:41 +0800
>> Subject: [V2] examples/vaapi_dec: Add a VA-API hwaccel decoding example.
>>
>> Add a VA-API hwaccel decoding example.
>>
>> Signed-off-by: Liu, Kaixuan <kaixuan.liu at intel.com>
>> Signed-off-by: Jun Zhao <jun.zhao at intel.com>
>> ---
>>  doc/examples/vaapi_dec.c | 266 +++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 266 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 0000000000..01320a3b71
>> --- /dev/null
>> +++ b/doc/examples/vaapi_dec.c
>> @@ -0,0 +1,266 @@
>> +/*
>> + * 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 <libavutil/pixdesc.h>
>> +#include <libavutil/hwcontext.h>
>> +#include <libavutil/opt.h>
>> +#include <libavutil/hwcontext_vaapi.h>
>> +#include <libavutil/avassert.h>
>> +
>> +static AVBufferRef *hw_device_ctx = NULL;
>> +FILE *output_file = NULL;
>> +
>> +int decoder_init_vaapi(AVCodecContext *ctx)
>> +{
>> +    int err = 0;
>> +    const char *dev_name = "/dev/dri/renderD128";
>> +
>> +    if ((err = av_hwdevice_ctx_create(&hw_device_ctx, AV_HWDEVICE_TYPE_VAAPI,
>> +                                      dev_name, NULL, 0)) < 0) {
> 
> The implementation already uses your dev_name as default, so you should
> be able to drop that, and pass NULL to it.
> 

Yes, will remove the dev_name.

>> +        fprintf(stderr, "Failed to create a VAAPI device.\n");
>> +        return err;
>> +    }
>> +    ctx->hw_device_ctx = av_buffer_ref(hw_device_ctx);
>> +
>> +    return err;
>> +}
>> +
>> +static enum AVPixelFormat get_vaapi_format(AVCodecContext *ctx,
>> +                                           const enum AVPixelFormat *pix_fmts)
>> +{
>> +    const enum AVPixelFormat *p;
>> +
>> +    for (p = pix_fmts; *p != -1; p++) {
>> +        if (*p == AV_PIX_FMT_VAAPI)
>> +            return *p;
>> +    }
>> +
>> +    return AV_PIX_FMT_NONE;
>> +}
>> +
>> +int retrieve_data(AVFrame *input)
>> +{
>> +    AVFrame *output = NULL;
>> +    int err;
>> +    av_assert0(input->format == AV_PIX_FMT_VAAPI);
>> +
>> +    if (!(output = av_frame_alloc()))
>> +        return AVERROR(ENOMEM);
>> +    /* default output nv12 */
>> +    output->format = AV_PIX_FMT_NV12;
> 
> You could use av_hwframe_transfer_get_formats() instead of hardcoding
> it. Might be better if the input is 10 bit, not sure. (Just a
> suggestion, up to you.)
Ok, it's will show the HW surface/ SW pixel format mapping if we 
use av_hwframe_transfer_get_formats() instead of hardcoding.

> 
>> +    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;
>> +        }
>> +    }
> 
> Using av_image_copy_to_buffer() would be more generic, although it'd
> require another allocation/copy in memory. (Just a suggestion.)
>
Will use av_image_copy_to_buffer().

>> +
>> +    return 0;
>> +}
>> +
>> +int decode_write(AVCodecContext *avctx, AVPacket packet, int flush)
>> +{
>> +    AVFrame *frame = NULL;
>> +    int ret = 0;
>> +
>> +    ret = avcodec_send_packet(avctx, &packet);
>> +    if (ret < 0 && ret != AVERROR_EOF)
>> +        return 0;
>> +
>> +    if (!(frame = av_frame_alloc()))
>> +        return AVERROR(ENOMEM);
>> +
>> +    ret = avcodec_receive_frame(avctx, frame);
>> +    if (ret >= 0) {
>> +        /* 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 == 0) {
>> +        ret = 0;
>> +    }
>> +
>> +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");
>> +        goto fail;
>> +    }
>> +
>> +    /* 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) {
>> +            video_stream = i;        /* NOTE: just handle the first video stream */
>> +            break;
>> +        }
>> +    }
>> +
>> +    if (video_stream == -1) {
>> +        fprintf(stderr, "No find a video stream in the input file.\n");
>> +        goto fail;
>> +    }
>> +
>> +    /* 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");
>> +        goto fail;
>> +    }
>> +
>> +    if (!(decoder_ctx = avcodec_alloc_context3(decoder)))
>> +        return AVERROR(ENOMEM);
>> +
>> +    if (avcodec_parameters_to_context(decoder_ctx,
>> +                                      input_ctx->streams[video_stream]->codecpar) < 0)
>> +        goto fail;
>> +
>> +    decoder_ctx->get_format  = get_vaapi_format;
>> +    av_opt_set_int(decoder_ctx, "refcounted_frames", 1, 0);
>> +
>> +    if (decoder_init_vaapi(decoder_ctx) < 0)
>> +        goto fail;
>> +
>> +    if ((ret = avcodec_open2(decoder_ctx, decoder, NULL)) < 0) {
>> +        fprintf(stderr, "Failed to open codec for stream #%u\n", i);
>> +        goto fail;
>> +    }
>> +
>> +    /* 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);
>> +
>> +fail:
>> +    if (output_file)
>> +        fclose(output_file);
>> +    avcodec_free_context(&decoder_ctx);
>> +    avformat_close_input(&input_ctx);
>> +    av_buffer_unref(&hw_device_ctx);
>> +
>> +    return ret;
>> +}
> 
> Generally looks OK. Can you replace all references to "vaapi" with "hw"
> or so? This code will work for other hwaccels too, and the only things
> that need to be switched are the AV_HWDEVICE_TYPE and the decoding
> AVPixelFormat. The pixel format still needs to be mapped manually, but
> we hope to add new API to make this also generic, so in the end you
> could choose the hw implementation by passing a name to it or fully
> automatically or so.

Good suggestion, will re-work for the general HWAccel decode sample.  
> Also please wait for comments by Mark Thompson.
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