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I want to re-encode the audio streams from mp2 to aac from one udp multicast MPEG TS Stream top another.

I have an udp multicast mpeg ts streram with 1 video, 3 audio, and 1 subtitles streams inside. I want to change the protocol of the audio streams from mp2 to aac. If ignore the subtitles stream everything is ok.

ffmpeg -re -i udp://224.2.2.42:1234 -map 0:0 -map 0:1 -map 0:2 -map 0:3 -c:v copy -c:a:0 libfdk_aac -c:a:1 libfdk_aac -c:a:2 libfdk_aac -f mpegts "udp://224.4.0.1:1234?pkt_size=1316"

Stream mapping:                                                                                                        
  Stream #0:0 -> #0:0 (copy)                                                                                           
  Stream #0:1 -> #0:1 (mp2 (native) -> aac (libfdk_aac))                                                               
  Stream #0:2 -> #0:2 (mp2 (native) -> aac (libfdk_aac))                                                               
  Stream #0:3 -> #0:3 (mp2 (native) -> aac (libfdk_aac))

and analyze with astra, everything is OK:

astra --analyze udp://224.4.0.1:1234
Jan 13 20:07:42: INFO: Bitrate: 6434 Kbit/s
Jan 13 20:07:43: INFO: Bitrate: 5821 Kbit/s
Jan 13 20:07:44: INFO: Bitrate: 3011 Kbit/s
Jan 13 20:07:45: INFO: Bitrate: 3536 Kbit/s
Jan 13 20:07:46: INFO: Bitrate: 1742 Kbit/s
Jan 13 20:07:47: INFO: Bitrate: 4460 Kbit/s
Jan 13 20:07:48: INFO: Bitrate: 3819 Kbit/s
Jan 13 20:07:49: INFO: Bitrate: 5915 Kbit/s
Jan 13 20:07:50: INFO: Bitrate: 4183 Kbit/s

But if I include and the Subtitles stream with this:

/ffmpeg -re -i udp://224.2.2.42:1234 -map 0:0 -map 0:1 -map 0:2 -map 0:3 -map 0:4 -c:v copy -c:s copy -c:a:0 libfdk_aac -c:a:1 libfdk_aac -c:a:2 libfdk_aac -f mpegts "udp://224.4.0.1:1234?pkt_size=1316"

Stream mapping:                                                                                                        
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (mp2 (native) -> aac (libfdk_aac))
  Stream #0:2 -> #0:2 (mp2 (native) -> aac (libfdk_aac))
  Stream #0:3 -> #0:3 (mp2 (native) -> aac (libfdk_aac))
  Stream #0:4 -> #0:4 (copy)

I got this with astra --analyze udp://224.4.0.1:1234

Jan 13 20:10:36: INFO: Bitrate: 0 Kbit/s
Jan 13 20:10:37: INFO: Bitrate: 11763 Kbit/s
Jan 13 20:10:38: INFO: Bitrate: 0 Kbit/s
Jan 13 20:10:39: INFO: Bitrate: 9198 Kbit/s
Jan 13 20:10:40: INFO: Bitrate: 1686 Kbit/s
Jan 13 20:10:41: INFO: Bitrate: 0 Kbit/s
Jan 13 20:10:42: INFO: Bitrate: 14344 Kbit/s
Jan 13 20:10:43: INFO: Bitrate: 1273 Kbit/s
Jan 13 20:10:44: INFO: Bitrate: 0 Kbit/s
Jan 13 20:10:45: INFO: Bitrate: 0 Kbit/s
Jan 13 20:10:46: INFO: Bitrate: 0 Kbit/s
Jan 13 20:10:47: INFO: Bitrate: 20570 Kbit/s
Jan 13 20:10:48: INFO: Bitrate: 0 Kbit/s
Jan 13 20:10:49: INFO: Bitrate: 11492 Kbit/s
Jan 13 20:10:50: INFO: Bitrate: 4231 Kbit/s
Jan 13 20:10:51: INFO: Bitrate: 0 Kbit/s
Jan 13 20:10:52: INFO: Bitrate: 0 Kbit/s

Can someone explain this and give me solution?

I just want to change the protocol of the audio streams from an UDP MPEG TS multicast stream from mp2 to aac and stream it to another multicast address like my example above. That's all

Ivan

Ivan Totev
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1 Answers1

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I found a solution. This is serious problem with ffmpeg and a good man from the ffmpeg chat room told me the solution. libavformat is known to wait for subtitles possibly for too long.

There is a patch for this:

https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200311213635.51736-1-rcombs@rcombs.me/

Without this patch ffmpeg "spits out" packets on periods when the input stream consists and subtitles track among the video/audio tracks

This patch in NOT included in Debian/Ubuntu's ffmpeg precompiled packages. You should apply it and compile ffmpeg from source !!!

Ivan Totev
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