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• flv from vlc to ffmpeg live video error when no sound temporarily

  14 septembre 2012, par dvch

  When we get live stream from vlc to ffmpeg , wherever there is sometimes 5-6 second no sound part of video , then ffmpeg is dead with this log

  flv @ 0x8b426d0]illegal ac vlc code at 4x6

  [flv @ 0x8b426d0]Error at MB : 142

  [flv @ 0x8b426d0]concealing 257 DC, 257 AC, 257 MV errors

  [mpegts @ 0x8b44e50]dts < pcr, TS is invalid

  Is there anyway to avoid this problem ?

• Is Java fast enough to do live screensharing ?

  10 mars 2012, par user1260501

  For the past few months, a developer and I have been working on a screensharing applet that streams to a media server like Wowza or Red5, but no matter what we do, we have about 5 seconds of latency, which is too long for a live application where people are interacting with each other. We've tried xuggle, different encoders, different players, different networks, different media servers, and even streaming locally, there's significant latency.

  So, I'm beginning to wonder…

  Is Java fast enough to do live screensharing ?

  I've seen lots of screen recording applets written in Java, but none of them are streaming live. Everything that's done live, such as GoToMeeting, seems to use C++. I'm thinking maybe there's a reason.

  It's not a compression problem. Using ScreenVideo, we've compressed an hour-long stream down to about 100 MB, and we have plenty of bandwidth. The processor isn't overloaded doing the compression, either, but it seems to be taking too much time. We are getting the best results from some code pulled out of BigBlueButton, but still, the latency is terrible.

  Streaming the WebCam, on the other hand, is nice and snappy. Almost no latency at all. So, the problem is the applet.

  The only other idea I can think of is somehow emulating a WebCam with Java. Not sure if that would be faster or not.

  Ideas ? Or should I just give up on Java and do this in C++ ? I would hate to do that, because then I would have to create different versions for different platforms, but if it's the only way, it's the only way.

• Generating 64kbps audio-only mpegts for HTTP Live segmenter to meept 64kbps audio only requirement

  23 avril 2012, par Pobre

  I am trying to convert our mp4 files into mpeg-ts and segment it into .ts files for my iphone app to play. I am using Carson McDonalds's HTTP-Live-Video-Stream-Segmenter-and-Distributor to do that.

  I got his stuff complied and working correctly. I am currently trying to meet Apple's requirement where I need to provide a baseline 64 kbps audio only stream to my m3u8 playlist.
  Carson doesn't seem to have a profile for that.

  I need to be able to generate 64kbps audio-only stream from mp4, and turn that into mpeg-ts for the segmenter into ts. I am trying to find the right ffmpeg command that will validate without problem using Apple's mediastreamvalidator.

  So far I modified an existing encoding profile to try to achieve 64kbps total :

  ffmpeg -er 4 -i %s -f mpegts -acodec libmp3lame -ar 22050 -ab 32k -s 240x180 -vcodec libx264 -b 16k -flags +loop+mv4 -cmp 256 -partitions +parti4x4+partp8x8+partb8x8 -subq 7 -trellis 1 -refs 5 -coder 0 -me_range 16 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -bt 64k -maxrate 16k -bufsize 16k -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 30 -aspect 4:3 -r 10 -g 30 -async 2 - | %s %s %s %s %s

  but then when I try to validate it using mediastreamvalidator, it gives error after few ts :

  Playlist Validation : OK

  Segments :

  sample_cell_4x3_64k-00001.ts :

  WARNING : Media segment exceeds target duration of 10.00 seconds by 1.30 seconds (segment duration is 11.30 seconds)

  sample_cell_4x3_64k-00002.ts :

  WARNING : Media segment exceeds target duration of 10.00 seconds by 1.40 seconds (segment duration is 11.40 seconds)

  ....
  ....

  sample_cell_4x3_64k-00006.ts :

  ERROR : (-1) Unknown video codec : 1836069494 (program 0, track 0)
  ERROR : (-1) failed to parse segment as either an MPEG-2 TS or an ES

  sample_cell_4x3_64k-00007.ts :

  ERROR : (-1) Unknown video codec : 1836069494 (program 0, track 0)
  ERROR : (-1) failed to parse segment as either an MPEG-2 TS or an ES

  ....
  ....
  Average segment duration : 10.26 seconds
  Average segment bitrate : 376797.92 bps
  Average segment structural overhead : 349242.17 bps (92.69 %)

  Is there someway I can generate this correctly with just audio which totals 64kbps and turn it into mpeg-ts ready to be segmented and validated correctly ?

  Am I approaching the problem right ?