[Asterisk-video] MP4Play async Audio / Video
Thomas Frieling
thomas.frieling at viif.de
Thu Sep 27 06:36:05 CDT 2007
Hi Sergio!
Sound is always OK and is always played perfectly. Video first is
synchronous, after that it often falls back (comes after the audio) and
sometimes catches up again. But this is only my impression - I cannot
say for sure.
I would propose that we add some debug messages to find out more:
- when a key-frame is actually sent to the handset we could print out
information on:
-> the current timestamp of the video-/audio-stream
-> the amount of waiting frames in the queue
-> other useful information?
Where would those debug commands go? Could someone create a patch/diff
for this (doesn't need to be committed to subversion I think...)?
Best Regards,
Thomas F
Am Dienstag, den 25.09.2007, 11:31 +0200 schrieb Sergio Garcia:
>
> What is the exact behaviour? The audio is delayed with video, but with a fixed delay?
> Is the video played at constant rate? Is the audio first, or the video??
> In the case of fixed delay the skewindication should solve the issue prefectly then.
>
> BR
> Sergio
>
> ---------- Original Message ----------------------------------
> From: Thomas Frieling <thomas.frieling at viif.de>
> Reply-To: Development discussion of video media support in Asterisk<asterisk-video at lists.digium.com>
> Date: Tue, 25 Sep 2007 11:17:01 +0200
>
> >Hi Sergio!
> >
> >I understand the problem with variable bitrates. The problem though is
> >that even videos that were recorded with a 3G handset and mp4save become
> >asynchronous when played back which is strange since this doesn't happen
> >on loopback...
> >That's why I think the "drop queued frames" option would be a nice
> >thing.
> >
> >What do you think?
> >Thomas F
> >
> >Am Dienstag, den 25.09.2007, 00:05 +0200 schrieb Sergio Garcia Murillo:
> >> Hi Thomas, Thomas and Ratmin.. :)
> >>
> >> Back to work form a long abroad weekend (nice Belgium!)
> >>
> >> As Ratmin has stated the Skew indication would help to indicate the
> >> handset the delay between audio and video.
> >> It's usually used to correct fixed delays introduced by internal
> >> jitter buffers and thinks alike. The problem that Thomas
> >> Z. is suffering seems to be produced by using ffmpeg for video
> >> encoding (as Thomas without Z points :)
> >> The problem is the following, ffmpeg is a great VBR (variable bit
> >> rate) encoder, but I've not been able to behave like a
> >> CBR (constant bit rate) encoder. The problem is that it's prepared for
> >> movies, not for streaming, and defenitevilly not
> >> at this low bitrates.
> >> The inner loop of the encoder always tries to encode ALL macroblocks
> >> in a frame, so in I frames and at a very low
> >> bitrate it simply just can't get a small amount of data for that frame
> >> and when it's enqued into h324m it takes more
> >> than one frame time to send (sometimes even more than a second), the
> >> following frames are small and sent after
> >> that until the queue is empty, which causes a fast-forward effect
> >> on some handsets. As you can imagine adjustime
> >> audio to that scenary is jus impossible (even with the Skew Indication
> >> the result would be horrible!!)
> >>
> >> The good solution: use a CBR encoder :)
> >> The not so good solution: drop packets when the queue is filled, but
> >> you'll end up dropping all the frames between
> >> each I frame.. but in that case it would be much better to lower the
> >> video fps...
> >>
> >> BR
> >> Sergio
> >> ----- Original Message -----
> >> From: Ramtin Amin
> >> To: Development discussion of video media support in Asterisk
> >> Sent: Monday, September 24, 2007 2:01 PM
> >> Subject: Re: [Asterisk-video] MP4Play async Audio / Video
> >>
> >>
> >>
> >>
> >>
> >> RTSP has timestamp... so you can usually know how to sync the
> >> audio/video
> >> But the problem would be more that we'll need to add a Skew
> >> Indication concept inside asterisk's core so it could make the
> >> message go throught the different channel/application, as it
> >> is currently done for VideoFastUpdatePicutre... Which means
> >> that currently, if a SIP channel receives a
> >> VideoFastUpdatePicture, it is capable of resending it to an
> >> other channel...
> >>
> >>
> >>
> >> ______________________________________________________________
> >>
> >> > Date: Mon, 24 Sep 2007 13:48:54 +0200
> >> > From: mobilemail at gmx-topmail.de
> >> > To: asterisk-video at lists.digium.com
> >> > Subject: Re: [Asterisk-video] MP4Play async Audio / Video
> >> >
> >> > Hello Ramin,
> >> > hello Thomas.
> >> >
> >> > I think both ways are possible. But I don't know if it easy
> >> to implement.
> >> > Sergio, what do you think about it?
> >> >
> >> > Is this also a problem if we stream the audi/video via rtsp?
> >> >
> >> > Regrads
> >> > Thomas
> >> >
> >> >
> >> > Ramtin Amin schrieb:
> >> > > hello
> >> > >
> >> > > The way I solved this problem was by sending a
> >> H223SkewIndication
> >> > > message to the other terminal
> >> > > Acutally, You will have to ask Sergio to add a H245
> >> indication message
> >> > > of type h223SkewIndication and when playing the video with
> >> mp4play, he
> >> > > will have to see the difference of timing between Video
> >> and Audio and
> >> > > then send this value to the remote terminal so the lip
> >> sync would work...
> >> > >
> >> > >
> >> > >
> >> > > **
> >> > >
> >> > > *2.3 Multipoint Lip Synchronization*
> >> > >
> >> > > In a multipoint VC, each terminal may transmit different
> >> > >
> >> > > //
> >> > >
> >> > > /H223SkewIndication /message for associated video and
> >> > >
> >> > > audio channels in H.223 protocol. To enable lip
> >> > >
> >> > > synchronization at receiving terminals, MCUs will
> >> > >
> >> > > transmit accurate /H223SkewIndication /messages. MCUs
> >> > >
> >> > > may accomplish this by adding delay to equalize the
> >> > >
> >> > > audio/video skew for all transmitting terminals. When
> >> > >
> >> > > switching between broadcasting terminals, H.223 may
> >> > >
> >> > > transmit a new /H223SkewIndication /message reflecting the
> >> > >
> >> > > audio/video skew of the current broadcaster.
> >> > >
> >> > >
> >> > > --
> >> > > Ramtin Amin
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> ------------------------------------------------------------------------
> >> > >
> >> > > > From: thomas.frieling at viif.de
> >> > > > To: asterisk-video at lists.digium.com
> >> > > > Date: Mon, 24 Sep 2007 11:48:12 +0200
> >> > > > Subject: Re: [Asterisk-video] MP4Play async Audio /
> >> Video
> >> > > >
> >> > > > Hi Thomas Z!
> >> > > >
> >> > > > I think this problem is due to the bitrate restriction
> >> on 3G calls. The
> >> > > > audio stream is always sent immediately while the video
> >> stream has to
> >> > > > use what is left of the bandwidth. This is why videos
> >> become synchrous
> >> > > > again when the video bitrate is pretty low for a while
> >> in the video...
> >> > > >
> >> > > > Take a look at this discussion:
> >> > > >
> >> > >
> >> http://lists.digium.com/pipermail/asterisk-video/2007-September/001257.html
> >> > > >
> >> > > > One solution is to reencode every video with a low
> >> bitrate and use a
> >> > > > fixed bitrate encoder (ffmpeg is dynamic bitrate for
> >> example). I had the
> >> > > > impression though that this still doesn't always work,
> >> especially when
> >> > > > the UMTS connection is not too good...
> >> > > >
> >> > > > My idea is that we check each time before sending a
> >> keyframe if there is
> >> > > > already a new keyframe in the queue. If this is the
> >> case, we jump to the
> >> > > > most recent keyframe and just drop the data before that.
> >> > > >
> >> > > > What do you think about this? How hard to implement?
> >> > > >
> >> > > > Regards,
> >> > > > Thomas F
> >> > > >
> >> > > >
> >> > > >
> >> > > > Am Montag, den 24.09.2007, 11:15 +0200 schrieb Thomas
> >> Z.:
> >> > > > > Hello,
> >> > > > >
> >> > > > > We have the problem, that a converted mp4 file is
> >> asynchronous via 3g
> >> > > > > network.
> >> > > > > If we play the file on a pc, everything is synchron.
> >> > > > > We tried already to reduce the quality and framerate
> >> of the video. But
> >> > > > > nothing helps.
> >> > > > >
> >> > > > > Is it a problem with mp4play or with the video?
> >> > > > >
> >> > > > > What can we do to get the audio and video synchronized
> >> via 3g network?
> >> > > > >
> >> > > > > Thank you,
> >> > > > > best regards
> >> > > > > Thomas
> >> > > > >
> >> > > > >
> >> > > > >
> >> > > > > _______________________________________________
> >> > > > > --Bandwidth and Colocation Provided by
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> >> > > > >
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> >> > > > >
> >> http://lists.digium.com/mailman/listinfo/asterisk-video
> >> > > > --
> >> > > > www.ViiF.de - your Mobile Video Community
> >> > > >
> >> > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >> > > >
> >> > > > Thomas Frieling - IT Development
> >> > > > ViiF Mobile Video GmbH, Poststr. 21-22, 10178 Berlin
> >> > > > Cell: +49 (0) 173 63 62 62 3
> >> > > >
> >> > > > mailto:thomas at ViiF.de
> >> > > >
> >> > > > Sitz: Berlin, Amtgericht Berlin-Charlottenburg, HRB:
> >> 108350B
> >> > > >
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> >> > > >
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> >> > >
> >> > >
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> >--
> >www.ViiF.de - your Mobile Video Community
> >
> >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> >Thomas Frieling - IT Development
> >ViiF Mobile Video GmbH, Poststr. 21-22, 10178 Berlin
> >Cell: +49 (0) 173 63 62 62 3
> >
> >mailto:thomas at ViiF.de
> >
> >Sitz: Berlin, Amtgericht Berlin-Charlottenburg, HRB: 108350B
> >
> >Geschäftsführer: Daniel Höpfner, Steffen Brünn
> >
> >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Fax: +49 30 22 50 50 63 9
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