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• Ignore streams when finding stream info

  17 mars 2018, par CSNewman

  I’m trying to speed up the start of ffmpeg when processing my live stream, and have narrowed down the issue to the ‘avformat_find_stream_info’ function. The source I’m trying to process seems to have a number of streams that ffmpeg is unable to determine what they are and therefore spends a while trying to find information about them (The entire analyse window). I know ahead of time that I only want to find information about stream #0:0 and #0:1, and I will be disregarding the other streams anyways.

  I managed to work around this using the API by setting the number of streams before the find information call and then restoring the value afterwards.

  inputContext->nb_streams = (uint) 2;
  
  if (ffmpeg.avformat_find_stream_info(inputContext, null) < 0)
  
  {
  
      throw new InvalidOperationException("Could not read stream information.");
  
  }
  
  inputContext->nb_streams = oldSize;

  However, I would prefer to use the CLI interface of ffmpeg.

  My current command

  ffmpeg -find_stream_info false -i http://192.168.1.112:5004/auto/v1 -c copy -map 0:v:0 -map 0:a:0 -ignore_unknown   -f hls -hls_flags delete_segments  -segment_list playlist.m3u8 -segment_list_type hls -segment_list_size 10 -segment_list_flags +live -segment_time 10 -f segment stream%%05d.ts

  Giving the following input (Unneeded logging removed)

  [mpeg2video @ 000001ce79423440] Invalid frame dimensions 0x0.
  
      Last message repeated 9 times
  
  [mpegts @ 000001ce7941b740] Could not find codec parameters for stream 5 (Unknown: none ([11][0][0][0] / 0x000B)): unknown codec
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  [mpegts @ 000001ce7941b740] Could not find codec parameters for stream 6 (Unknown: none ([11][0][0][0] / 0x000B)): unknown codec
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  [mpegts @ 000001ce7941b740] Could not find codec parameters for stream 7 
  
  (Unknown: none ([5][0][0][0] / 0x0005)): unknown codec
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  [mpegts @ 000001ce7941b740] Could not find codec parameters for stream 8 
  
  (Unknown: none ([5][0][0][0] / 0x0005)): unknown codec
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  Input #0, mpegts, from 'http://192.168.1.112:5004/auto/v1':
  
    Duration: N/A, start: 91296.182311, bitrate: N/A
  
    Program 4165
  
      Stream #0:0[0x65]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv, top first), 704x576 [SAR 16:11 DAR 16:9], 25 fps, 25 tbr, 90k tbn, 50 tbc
  
      Stream #0:1[0x66](eng): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, s16p, 256 kb/s
  
      Stream #0:2[0x6a](eng): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, mono, s16p, 64 kb/s (visual impaired) (dependent)
  
      Stream #0:3[0x69](eng): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006)
  
      Stream #0:4[0x98]: Audio: mp2 ([6][0][0][0] / 0x0006), 48000 Hz, stereo, s16p, 128 kb/s
  
      Stream #0:5[0x1c21]: Unknown: none ([11][0][0][0] / 0x000B)
  
      Stream #0:6[0x1c33]: Unknown: none ([11][0][0][0] / 0x000B)
  
      Stream #0:7[0x1bbf]: Unknown: none ([5][0][0][0] / 0x0005)
  
      Stream #0:8[0x1bc1]: Unknown: none ([5][0][0][0] / 0x0005)

  I’m unsure if there’s a way to achieve the same functionality with the CLI, however I’m open changing how my setup works.

  One idea that I considered was running two ffmpeg instances, one to strip the unneeded streams (and not find the stream info) and then have another that takes that stripped stream and performs the rest of the functionality.

  Any insight here would be grateful, thanks in advance.

• How to parse WMV (ASF) file ? Can't find length of data packets

  9 mars 2018, par bukkojot

  I try to parse WMV (ASF) files without any SDK, just by decoding raw bytes. Now I have problem with ASF_Data_Object, where I can’t find length of data packet. More precise, Single payload data packet.

  See image :
  

  Here I have 9 packets, but unable to find size of individual packet. How I can determine border between packets ?

  I think, my problem at byte 0x411, where field "Length type flags". As you can see, here 0 value, so all flags are zero. Even Packet Length Type.

  
  

  Yes, 0 value here allowed here. But how to read this type of content ?

  This is now compressed payload, as replication data is 8, not 1. So, this is single payload without additional fields of size.

  Sample of WMV file : https://files.catbox.moe/b51l2j.wmv

• Why does my video have an audio/mp4 mime type [duplicate]

  22 février 2018, par Tucker Peebles

  This question already has an answer here :

  • How do you safely identify whether an mp4 is an audio only or video file
    
    1 answer
    
  • Using ffprobe to check audio-only files
    
    3 answers
    

  I have a video file but it has a mime type of "audio/mp4". Why would that happen. The user who sent it to me said it came from a Flip video camera and was uploaded by usb to her computer.

  In my program, I’m checking for ’video/mp4’ mime type when I’m trying to determine if it’s a video, but I want to eventually support audio uploads too which would need to check ’audio/mp4’.

  Unfortunately, the video is a personal video of the user’s child so I don’t want to upload it here. Let me know if there is any information I can provide about the video that would help.