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

[Anton Shekhovtsov]

ср, 3 окт. 2018 г. в 13:31, Niraj Gandha <niraj.gandha at einfochips.com>:

> Use below code and might help you in solving your problem.
>
> while (av_read_frame(refrenceFormatCtx, &packet) >= 0) {
>
> if (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_index = stream->id;
> int result = avcodec_decode_video2(codec_ctx, picture_yuv, &check,
> &packet);
>
> av_free_packet(&packet);
>
> av_packet_unref(&packet);
>
> if(result <= 0 || check == 0){
>
> continue;
>
> }
>
> 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);
> initialize_rgb_requirements=0;
>
> }
>
> 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);
>
> }
> }
>
> Get Outlook for Android <https://aka.ms/ghei36>
>
> ------------------------------
> *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:
> https://ffmpeg.org/doxygen/4.0/group__lavc__encdec.html
>
> avcodec_send_packet
> avcodec_receive_frame
>
> And for context we setup:
> context->err_recognition = AV_EF_EXPLODE | AV_EF_BITSTREAM | AV_EF_BUFFER
> | AV_EF_CAREFUL | AV_EF_COMPLIANT | AV_EF_AGGRESSIVE;
>
>
> ср, 3 окт. 2018 г. в 12:58, Niraj Gandha <niraj.gandha at einfochips.com>:
>
>> Hi Vasiliy,
>>
>> Can you share the code in which you are decoding the stream?
>>
>> Thanks,
>> Niraj Gandha
>>
>> Get Outlook for Android <https://aka.ms/ghei36>
>>
>> ------------------------------
>> *From:* Libav-user <libav-user-bounces at ffmpeg.org> on behalf of Vasiliy
>> Volkov <volk.vasiliy at gmail.com>
>> *Sent:* Wednesday, October 3, 2018 3:08:08 PM
>> *To:* libav-user at ffmpeg.org
>> *Subject:* [External] [Libav-user] Questions about decoding broken
>> streams
>>
>> CAUTION: This email originated from outside of the organization. Do not
>> click links or open attachments unless you recognize the sender and know
>> the content is safe.
>>
>> Hi,
>>
>> 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.
>>
>> Thanks
>> *************************************************************************************************************************************************************
>> eInfochips Business Disclaimer: This e-mail message and all attachments
>> transmitted with it are intended solely for the use of the addressee and
>> may contain legally privileged and confidential information. If the reader
>> of this message is not the intended recipient, or an employee or agent
>> responsible for delivering this message to the intended recipient, you are
>> hereby notified that any dissemination, distribution, copying, or other use
>> of this message or its attachments is strictly prohibited. If you have
>> received this message in error, please notify the sender immediately by
>> replying to this message and please delete it from your computer. Any views
>> expressed in this message are those of the individual sender unless
>> otherwise stated. Company has taken enough precautions to prevent the
>> spread of viruses. However the company accepts no liability for any damage
>> caused by any virus transmitted by this email.
>> *************************************************************************************************************************************************************
>>
>> _______________________________________________
>> Libav-user mailing list
>> Libav-user at ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/libav-user
>>
> _______________________________________________
> Libav-user mailing list
> Libav-user at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/libav-user


What you wanted to show with this example? That's true, some (or all)
decoders don't return errors.
Example in ffv1dec.c
                av_log(f->avctx, AV_LOG_ERROR, "CRC mismatch %X!", crc);
No error code returned from here. It is possible to abuse log hook somehow.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://ffmpeg.org/pipermail/libav-user/attachments/20181003/4faebb69/attachment.html>