[Libav-user] [External] Questions about decoding broken streams

Niraj Gandha niraj.gandha at einfochips.com
Wed Oct 3 13:31:15 EEST 2018

Use below code and might help you in solving your problem.

while (av_read_frame(refrenceFormatCtx, &packet) >= 0) {

if (packet.stream<http://packet.stream/>_index == video_stream_index) { //packet is video

if (stream == NULL) { //create stream in file

stream = avformat_new_stream(output_ctx, refrenceFormatCtx->streams[video_stream_index]->codec->codec);

avcodec_copy_context(stream->codec, refrenceFormatCtx->streams[video_stream_index]->codec);

stream->sample_aspect_ratio = refrenceFormatCtx->streams[video_stream_index]->codec->sample_aspect_ratio;

int check = 0;
 packet.stream<http://packet.stream/>_index = stream->id;
int result = avcodec_decode_video2(codec_ctx, picture_yuv, &check, &packet);



if(result <= 0 || check == 0){



if(initialize_rgb_requirements) {

sizeofrgbpicture = avpicture_get_size(AV_PIX_FMT_RGB24, codec_ctx->width, codec_ctx->height);

picture_rgb = av_frame_alloc();

picture_buffer_rgb = (uint8_t*) (av_malloc(sizeofrgbpicture));

avpicture_fill((AVPicture *) picture_rgb, picture_buffer_rgb, AV_PIX_FMT_RGB24, codec_ctx->width, codec_ctx->height);

img_convert_ctx = sws_getContext(codec_ctx->width, codec_ctx->height, AV_PIX_FMT_YUV420P, codec_ctx->width, codec_ctx->height,AV_PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);


int height = 0;

if(picture_yuv->data != NULL) {
height = sws_scale(img_convert_ctx, ((AVPicture*)picture_yuv)->data, ((AVPicture*)picture_yuv)->linesize, 0, codec_ctx->height, ((AVPicture*)picture_rgb)->data,((AVPicture*)picture_rgb)->linesize);


rgb_image_data = (uint8_t *)malloc(sizeofrgbpicture * sizeof(uint8_t));

int ret = avpicture_layout((AVPicture *)picture_rgb, AV_PIX_FMT_RGB24, codec_ctx->width, codec_ctx->height, rgb_image_data, sizeofrgbpicture);

emit imageQueued(rgb_image_data, codec_ctx->width,codec_ctx->height);


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From: Libav-user <libav-user-bounces at ffmpeg.org> on behalf of Vasiliy Volkov <volk.vasiliy at gmail.com>
Sent: Wednesday, October 3, 2018 3:44:49 PM
To: libav-user at ffmpeg.org
Subject: Re: [Libav-user] [External] Questions about decoding broken streams

Well there is no anything unusual in our code. We're simply use this API:


And for context we setup:

ср, 3 окт. 2018 г. в 12:58, Niraj Gandha <niraj.gandha at einfochips.com<mailto:niraj.gandha at einfochips.com>>:
Hi Vasiliy,

Can you share the code in which you are decoding the stream?

Niraj Gandha

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From: Libav-user <libav-user-bounces at ffmpeg.org<mailto:libav-user-bounces at ffmpeg.org>> on behalf of Vasiliy Volkov <volk.vasiliy at gmail.com<mailto:volk.vasiliy at gmail.com>>
Sent: Wednesday, October 3, 2018 3:08:08 PM
To: libav-user at ffmpeg.org<mailto:libav-user at ffmpeg.org>
Subject: [External] [Libav-user] Questions about decoding broken streams

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I'm trying to deal with broken streams with libav. Sometimes streams can be broken due to nature of incoming network channel (UDP multicast) but i'd like to "fix them" as much as possible. I'm trying to fill broken frames with last good decoded frame. There are situations when I can do such thing and everything is ok but most of time it's not helping: libav tries to decode broken stream and add some green frames (h264 decoding) which really catch your eyes when you watch this stream after encoding.
Is it possible to change this color to black for example? Can libav while decoding set some flags to frames and mark them as broken or "green"?
It will be helpful because next I'll can replace such frames with correctly decoded which fix it.

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