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• Past duration 0.750206 too large when capturing my screen

  2 avril 2018, par it_is_a_literature

  I want to capture my screen with ffmpeg

  xrandr
  
  Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
  
  ffmpeg -f x11grab -framerate 30 -threads 0 -s 1920 x 1080 -i :0 /tmp/capture.mp4

  Error info :

  [x11grab @ 0x556025373ae0] Stream #0: not enough frames to estimate rate; consider increasing probesize
  
  Past duration 0.750206 too large     435kB time=00:00:01.00 bitrate=3564.5kbits/s dup=19 drop=0 speed=0.382x    
  
  Past duration 0.749168 too large

  Try other ffmpeg command.

  ffmpeg -f x11grab -video_size 1360x768 -framerate 30 -i :0.0 -f pulse -i default -preset ultrafast -crf 18 -pix_fmt yuv420p out.mkv
  
  
  
  [x11grab @ 0x55db2f72fc00] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
  
  [pulse @ 0x55db2f7374e0] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
  
  [output stream 0:1 @ 0x55db2f7784e0] 100 buffers queued in output stream 0:1, something may be wrong.
  
  [libvorbis @ 0x55db2f753720] Queue input is backward in time
  
  [matroska @ 0x55db2f750760] Non-monotonous DTS in output stream 0:1; previous: 3411, current: 3272; changing to 3411. This may result in incorrect timestamps in the output file.

  How to fix it ?

• mp4 plays only sound but no video on ios

  5 avril 2018, par Chen

  I have a video that I get from a third party provide in my App, I want to play using react-native-video. It works fine on simulator, but on a real iphone 7 it has only sound but no video.

  After further research I found, when I try to airdrop/move via itunes the video to my iphone. It shows something like the following :

  

  I have checked the codec with ffprobe and here is the output.
  ```

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'bad.mp4':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: mp42mp41
  
      creation_time   : 2018-03-28T21:30:13.000000Z
  
    Duration: 00:00:45.55, start: 0.000000, bitrate: 1373 kb/s
  
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 1042 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
      Metadata:
  
        creation_time   : 2018-03-28T21:30:13.000000Z
  
        handler_name    : Alias Data Handler
  
        encoder         : AVC Coding
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 317 kb/s (default)
  
      Metadata:
  
        creation_time   : 2018-03-28T21:30:13.000000Z
  
        handler_name    : Alias Data Handler
  
  [STREAM]
  
  index=0
  
  codec_name=h264
  
  codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
  
  profile=High
  
  codec_type=video
  
  codec_time_base=1001/60000
  
  codec_tag_string=avc1
  
  codec_tag=0x31637661
  
  width=1920
  
  height=1080
  
  coded_width=1920
  
  coded_height=1080
  
  has_b_frames=1
  
  sample_aspect_ratio=1:1
  
  display_aspect_ratio=16:9
  
  pix_fmt=yuv420p
  
  level=41
  
  color_range=tv
  
  color_space=bt709
  
  color_transfer=bt709
  
  color_primaries=bt709
  
  chroma_location=left
  
  field_order=unknown
  
  timecode=N/A
  
  refs=1
  
  is_avc=true
  
  nal_length_size=4
  
  id=N/A
  
  r_frame_rate=30000/1001
  
  avg_frame_rate=30000/1001
  
  time_base=1/30000
  
  start_pts=0
  
  start_time=0.000000
  
  duration_ts=1365364
  
  duration=45.512133
  
  bit_rate=1042237
  
  max_bit_rate=N/A
  
  bits_per_raw_sample=8
  
  nb_frames=1364
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  DISPOSITION:default=1
  
  DISPOSITION:dub=0
  
  DISPOSITION:original=0
  
  DISPOSITION:comment=0
  
  DISPOSITION:lyrics=0
  
  DISPOSITION:karaoke=0
  
  DISPOSITION:forced=0
  
  DISPOSITION:hearing_impaired=0
  
  DISPOSITION:visual_impaired=0
  
  DISPOSITION:clean_effects=0
  
  DISPOSITION:attached_pic=0
  
  DISPOSITION:timed_thumbnails=0
  
  TAG:creation_time=2018-03-28T21:30:13.000000Z
  
  TAG:language=eng
  
  TAG:handler_name=Alias Data Handler
  
  TAG:encoder=AVC Coding
  
  [/STREAM]
  
  [STREAM]
  
  index=1
  
  codec_name=aac
  
  codec_long_name=AAC (Advanced Audio Coding)
  
  profile=LC
  
  codec_type=audio
  
  codec_time_base=1/48000
  
  codec_tag_string=mp4a
  
  codec_tag=0x6134706d
  
  sample_fmt=fltp
  
  sample_rate=48000
  
  channels=2
  
  channel_layout=stereo
  
  bits_per_sample=0
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/48000
  
  start_pts=0
  
  start_time=0.000000
  
  duration_ts=2184582
  
  duration=45.512125
  
  bit_rate=317375
  
  max_bit_rate=458625
  
  bits_per_raw_sample=N/A
  
  nb_frames=2135
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  DISPOSITION:default=1
  
  DISPOSITION:dub=0
  
  DISPOSITION:original=0
  
  DISPOSITION:comment=0
  
  DISPOSITION:lyrics=0
  
  DISPOSITION:karaoke=0
  
  DISPOSITION:forced=0
  
  DISPOSITION:hearing_impaired=0
  
  DISPOSITION:visual_impaired=0
  
  DISPOSITION:clean_effects=0
  
  DISPOSITION:attached_pic=0
  
  DISPOSITION:timed_thumbnails=0
  
  TAG:creation_time=2018-03-28T21:30:13.000000Z
  
  TAG:language=eng
  
  TAG:handler_name=Alias Data Handler
  
  [/STREAM]

  Then I tried VLC on iOS the video played without problem (it has both video and sound), except at the beginning it shows a grey pixel screen.

  

  Next, what i did was using ffmpeg to re-encode the video stream via :

  ffmpeg -i bad.mp4 -c:a copy new.mp4

  After this new.mp4 plays with no problem.
  This is really confusing as the codec does not change and both videos works with no problem on my Mac.

  I have tried to play around with the b_frames, profile level on the new video to reproduce the problem but with no luck.

  I really do not want to process every video via ffmpeg after get it from the third party. Just wondering what might be the problem with the video ?

• FFMPEG corrupted frame when streaming in UDP (MPEGTS)

  17 décembre 2020, par user37616

  I am working on a screen streaming program, till now, I can capture and encode my screen into a video perfectly. 
However, whenever I try to stream it over LAN, and play using Mplayer, it is able to run in simple desktop (text document, etc...) but when I try to play video the frame stated to corrupted until I quit the video (this video cause the most corrupted frame https://www.youtube.com/watch?v=1La4QzGeaaQ&t=230s)

  



  I am not really sure why when streaming, I got corrupted frame with the youtube video but when save it to a file (change URL from udp ://192.168.1.xxx:YYYY to file name C :\Test.ts) there were no corrupted frame at all.
 My Mplayer log :

  



  `V:   0.0 1563/1563 51% 43%  0.0% 0 0
[h264 @ 0000000001d04940]Invalid NAL unit 0, skipping.
[h264 @ 0000000001d04940]error while decoding MB 23 51, bytestream -64
[h264 @ 0000000001d04940]concealing 2066 DC, 2066 AC, 2066 MV errors in I frame
V:   0.0 1564/1564 51% 43%  0.0% 0 0
[h264 @ 0000000001d04940]concealing 7598 DC, 7598 AC, 7598 MV errors in P frame
V:   0.0 1652/1652 50% 43%  0.0% 0 0
[h264 @ 0000000001d04940]Invalid NAL unit 0, skipping.
[h264 @ 0000000001d04940]error while decoding MB 26 49, bytestream -55
[h264 @ 0000000001d04940]concealing 2303 DC, 2303 AC, 2303 MV errors in I frame
V:   0.0 1653/1653 50% 43%  0.0% 0 0
[h264 @ 0000000001d04940]concealing 7727 DC, 7727 AC, 7727 MV errors in P frame
V:   0.0 1741/1741 49% 43%  0.0% 0 0
[h264 @ 0000000001d04940]Invalid NAL unit 0, skipping.
[h264 @ 0000000001d04940]error while decoding MB 65 62, bytestream -57
[h264 @ 0000000001d04940]concealing 704 DC, 704 AC, 704 MV errors in I frame
V:   0.0 1742/1742 49% 43%  0.0% 0 0`


  



  Stream initialize code

  



  static void Stream_ini(const char *Url, AVFormatContext *&ofmt_ctx, AVCodec *codec, AVCodecContext *c, AVStream *&out_stream)
{
    int ret;


    avformat_alloc_output_context2(&ofmt_ctx, NULL, "mpegts", Url);
    out_stream = avformat_new_stream(ofmt_ctx, codec)
    out_stream->codec = c;
    av_dump_format(ofmt_ctx, 0, Url, 1);


    if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
        out_stream->codec->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
    if (!(ofmt_ctx->flags & AVFMT_NOFILE))
    {
        ret = avio_open(&ofmt_ctx->pb, Url, AVIO_FLAG_WRITE);
        if (ret < 0)
        {
            printf("Could not open output URL '%s'", Url);
            return;
        }
    }


    ret = avformat_write_header(ofmt_ctx, NULL);

    if (ret < 0)
    {
        printf("Error occurred when opening output URL\n");
        return;
    }


}


  



  this code will get the captured screen and send it to encoder :

  



  ScreenCap.load_screen_data(inFrame,timmer)  // this will capture screen and return the time and AVFrame for encoding
sws_scale(ctx, inFrame->data, inFrame->linesize, 0,c->height, frame->data, frame->linesize);

frame->pts = (timmer - first_frame_time) / fps;
EncodeToPkT(c, frame, pkt, ofmt_ctx,out_stream);

av_frame_free(&inFrame);


  



  the AVFrame will then be send to encoder using avcodec_send_frame() to get Packet data and av_interleaved_write_frame() to stream it over LAN.

  



  All error check are removed for simplicity

  



  Also, this is my AVCodecContex setting for the encoder :

  



  c->bit_rate = 15000000;
c->width = 1920;
c->height = 1080;
c->time_base = AVRational{ 1, 90 };
c->framerate = AVRational{ 90, 1 };
c->gop_size = 90;
c->max_b_frames = 0;
c->pix_fmt = AV_PIX_FMT_RGB0;


  



  I also notice it only happen when I increase encoder bitrate (15 MBIT) but when lower it down to (10 MBIT) it happen less. And when lower it down to 2 MBIT the corrupted frame not happen anymore however the quality is really bad.
  
I test the streaming in LAN using : PC -> cable ->laptop, PC->wireless->laptop, PC->Virtual PC, PC only (enter PC IP address in both program and Mplayer), all got the same result.

  



  I also test my DXGICap.load_screen_data function by make it output raw image and there were no corrupted image at all

  



  Does anybody have an idea why.

  



  Thank Nam.