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

Mark Thompson sw at jkqxz.net
Wed Jul 19 02:30:15 EEST 2017


On 17/07/17 03:51, Jun Zhao wrote> 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>

This file is deprecated, and contains nothing useful anyway.

>>> +#include <libavformat/avformat.h>
>>> +#include <libavutil/pixdesc.h>
>>> +#include <libavutil/hwcontext.h>
>>> +#include <libavutil/opt.h>
>>> +#include <libavutil/hwcontext_vaapi.h>

Shouldn't need any of the API-specific hwcontext includes, just the generic one.

>>> +#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)

I don't think you mean to pass the packet by value here.

>>> +{
>>> +    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;

IIRC passing NULL directly to avcodec_send_packet() is preferable to an empty packet to flush?

>>> +
>>> +    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;
>>> +        }
>>> +    }

Maybe replace this block with av_find_best_stream()?  (Assuming there isn't some reason I'm missing that that doesn't work...)

>>> +
>>> +    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.

Agree.  Maybe pass the type name as a first argument to make the command line like "argv[0] <vaapi|dxva2|d3d11va> <input file> <output file>"?

(Those three should work at least.  Videotoolbox might work as well, VDPAU would need different output formats.  Probably don't want more complexity than that, though, because it wants to be a clear example.)

Rest looks good to me.

Thanks,

- Mark


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