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Thread: LATM DePacketizer problem

  1. Default LATM DePacketizer problem

    we have a problem in wowza, (either with transcoder addon or not)
    when incoming audio has LATM filter (latm_aac), after wowza we have no sound.

    source signal (H.264 and AAC_LATM) came from SAT, we have an gateway and send stream in MPEG_TS over RTP to wowza for restreaming.
    VLC plays incoming RTP stream perfectly and shows the audio codec is mp4a_latm.
    also ffmpeg shows the audio codec is latm_aac.

    but after wowza there is no sound in output stream.
    in same scenario when incoming audio stream is pure aac everything works fine.
    so we are doubtful that wowza cannot depacketize LATM audio.
    in log we found out that MPEGTSDePacketizer is used.

    when using transcoder no audio decoder is build. the cause may reside in inappropriate DePacketizer chosen by wowza.

    would you please help us and tell us what should we do for LATM audio DePacketizer.
    thanks in advance.

  2. #2
    Join Date
    Jun 2012



    Some MPEG-TS encoders publish audio and video where the media frames aren't aligned on PES packet boundaries. This will cause the audio and video to not play.
    Please take a look at this article on how to add the audioIsAligned property to your application configuration file.


  3. Default

    Thanks for your reply.
    but it doesn't work.
    i try both audioIsAligned True and False. but output stream from wowza doesn't have audio stream at all.
    please note that VLC can play stream perfectly just before wowza.

  4. Default

    i can send you a small sample of my incoming video which captured by VLC.
    another consideration is that VLC show audio stream has SBR+PS AAC Extension.

  5. #5
    Join Date
    Jun 2012



    I noticed that you have opened a ticket with our ticketing system (ticket #70272). Can you please provide my colleague with the captures he is asking for?
    Can you tell me what are the audio encoding parameters? I know it's AAC, but what are the bitrate and sample rate values?


  6. Default

    Thanks for your reply
    ticket updated as you want,
    here is output from ffmpeg -i

    Seems stream 0 codec frame rate differs from container frame rate: 50.00 (50/1) -> 50.00 (50/1)
    Input #0, mpegts, from 'udp://':
    Duration: N/A, start: 2739.401533, bitrate: N/A
    Program 101
    Stream #0.0[0x3f2]: Video: h264 (Main), yuv420p, 720x576 [PAR 12:11 DAR 15:11], 54.40 fps, 50 tbr, 90k tbn, 50 tbc
    Stream #0.1[0x3f3](per): Audio: aac_latm, 48000 Hz, 2 channels (FC), s16 (clean effects)

    please let me know if you need something else.

  7. Unhappy

    Any update???

  8. #8



    I did reply to your ticket directly.

    The stream is missing ADTS Headers on the audio stream. Without these headers, Wowza is unable to process the stream properly.



  9. Default

    Any chance to wowza will handle this kind of stream in near future,
    or maybe create a patch for this???

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