[Asterisk-video] MP4Play async Audio / Video
Thomas Z.
mobilemail at gmx-topmail.de
Tue Sep 25 03:52:07 CDT 2007
Hello Sergio,
do you know a freeware or cheap CBR encoder?
Regards
Thomas
Sergio Garcia Murillo schrieb:
> 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 <mailto:keytwho at hotmail.com>
> *To:* Development discussion of video media support in Asterisk
> <mailto:asterisk-video at lists.digium.com>
> *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
> > > > >
> > > > >
> > > > >
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> > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >
> > > > Thomas Frieling - IT Development
> > > > ViiF Mobile Video GmbH, Poststr. 21-22, 10178 Berlin
> > > > Cell: +49 (0) 173 63 62 62 3
> > > >
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> > > >
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