[Asterisk-video] aac audio

francesco francesco.emmi at a-tono.com
Wed Apr 18 02:06:11 MST 2007 

Hi all,

Analyzing h223 flows, my suspect is that audio problem is the inverse of
what we can imagine. It is sent too slowly and not the inverse.

So, just to make a simple test I' ve modified function mp4_rtp_read to
return 18 (instead of correct value 20) when dealing with audio frame.
This speeds up audio output.

The result is definitely a good quality on Nokia. Just like Samsung.

A work around should be to hint mp4 file using -timescale option (and
probably some few more lines in app_mp4) just to speed up audio, and use
this trick together with new Sergio jitter buffer.

But optimum is to understand why audio sdu is sent slower than 1 each 20
ms as it should be (as app_mp4 reads a audio frame each 20 ms...)

Greetings
Francesco

On Tue, 2007-04-17 at 02:12 +0200, Sergio Garcia Murillo wrote:
> I've just updated the svn with a new version.
> I've implemented a simple jitter buffer for the audio channel. Now it won't
> start muxing audio until it get a minimun size on the
> buffer and then continue sending packets with a minimum delay between each
> one.
> I don't know if it's going or work or not, so any feedback would be very
> valuable. You can change the values on the audio channel
> constructor to see if we make it behave better.
> H324MAudioChannel(3,160);
> 
> Greetings
> Sergio
> 
> ----- Original Message ----- 
> From: "René van Weert" <rvweert at gmail.com>
> To: "'Development discussion of video media support in Asterisk'"
> <asterisk-video at lists.digium.com>
> Sent: Monday, April 16, 2007 4:05 PM
> Subject: RE: [Asterisk-video] aac audio
> 
> 
> Dear Francesco,
> 
> I could also be that you have better/faster hardware than I do. I am running
> on a P4 1.8Ghz with 512mb ram. This might be too low at the moment to
> process the incoming video and therefore cause in my case the audio to sound
> corrupted. On what system are you running?
> 
> With kind regards,
> 
> René
> 
> -----Oorspronkelijk bericht-----
> Van: asterisk-video-bounces at lists.digium.com
> [mailto:asterisk-video-bounces at lists.digium.com] Namens francesco
> Verzonden: maandag 16 april 2007 11:06
> Aan: Development discussion of video media support in Asterisk
> Onderwerp: RE: [Asterisk-video] aac audio
> 
> Hi Renè,
> 
> I' ve tried to switch off sending audio and video, but I experienced
> only a very few improvement of quality. Quite far from that of other
> handyset (e.g. Samsung).
> 
> More over, if mean problem were CPU load due to input video and audio,
> probably we would experience same result on every handset and no only on
> Nokia.
> 
> For sure optimization is a good choice but to solve definitely audio
> problem my opinion is that we must investigate on other stuffes
> 
> Francesco
> 
> On Sun, 2007-04-15 at 12:18 +0200, René van Weert wrote:
> > Hi,
> >
> > I see indeed that the CPU load goes way down if I switch off sending
> audio/video on the mobile. Isn't there a way to disable the processing of
> this incoming audio/video on Asterisk?
> >
> > Greetings,
> >
> > RvW
> >
> > -----Oorspronkelijk bericht-----
> > Van: asterisk-video-bounces at lists.digium.com
> [mailto:asterisk-video-bounces at lists.digium.com] Namens Sergio Garcia
> Murillo
> > Verzonden: vrijdag 13 april 2007 1:59
> > Aan: Development discussion of video media support in Asterisk
> > Onderwerp: Re: [Asterisk-video] aac audio
> >
> > Probably, when turning off audio and video on nokia, less processing is
> > needed so you get less lagg.
> > I think it's time for optimization.. :)
> >
> > Greetings
> > Sergio
> >
> > ----- Original Message ----- 
> > From: "René van Weert" <rvweert at gmail.com>
> > To: "'Development discussion of video media support in Asterisk'"
> > <asterisk-video at lists.digium.com>
> > Sent: Thursday, April 12, 2007 8:39 PM
> > Subject: RE: [Asterisk-video] aac audio
> >
> >
> > Hi Francesco and Sergio,
> >
> > Thank you both for the advice. I tried now with audio at 12k and video at
> > 50k. I also recompiled with -O3. On other phones the sound is better
> already
> > but on my nokia n80 it still is a little blurry. Ff I turn of sending
> video
> > and audio from the phone however the incoming audio quality improves quite
> a
> > lot. Might this be something related to the problem?
> >
> > With kind regards,
> >
> > René
> >
> > -----Oorspronkelijk bericht-----
> > Van: asterisk-video-bounces at lists.digium.com
> > [mailto:asterisk-video-bounces at lists.digium.com] Namens francesco
> > Verzonden: donderdag 12 april 2007 9:59
> > Aan: Development discussion of video media support in Asterisk
> > Onderwerp: RE: [Asterisk-video] aac audio
> >
> > Hi Renè,
> >
> > Try to hint audio track indicating also payload size:
> >
> > mp4creator --hint=2 -mtu=64 dest.mp4
> >
> > I suggest you also to follow Sergio tip to compile with -O3 option. You
> > may also use amr mode 8, with ffmpeg option -ab 12K...lowering bit rate
> > doesn't give me any result, so I don' t think it is a good choice.
> >
> > Quality should be much better. But still not good in Nokia N80 as in
> > other handset.
> >
> > I'm working on it and let you know as soon as I have news.
> >
> > Greetings
> > Francesco
> >
> > On Wed, 2007-04-11 at 19:03 +0200, René van Weert wrote:
> > > Hi,
> > >
> > > I mistakenly used AAC indeed. I am now back to amr-nb which is working,
> > but
> > > not 100% correct.
> > > I put up a sound sample of how it sounds on my Nokia N80 here:
> > > http://www.digitalinteraction.nl/downloads/audiosample.mp3
> > >
> > > Is it because there is still some work to do or because I am doing
> > something
> > > wrong the audio sounds so wrong?
> > >
> > > I have used ffmpeg to convert my media file as follows:
> > > ffmpeg -i woning2.wmv -ab 7.4k -ac 1 -acodec amr_nb -ar 8000 -vcodec
> > h263 -r
> > > 10 -s qcif -b 46K -pass 1 -passlogfile log dest.mp4
> > > ffmpeg -i woning2.wmv -ab 7.4k -ac 1 -acodec amr_nb -ar 8000 -vcodec
> > h263 -r
> > > 10 -s qcif -b 46K -pass 2 -passlogfile log dest.mp4
> > >
> > > mp4creator --hint=1 dest.mp4
> > > mp4creator --hint=2 dest.mp4
> > >
> > > The destination file is available here:
> > > http://www.digitalinteraction.nl/downloads/dest.mp4
> > > Mp4info gives:
> > > Track   Type    Info
> > > 1       video   H.263, 77.500 secs, 44 kbps, 176x144 @ 10.000000 fps
> > > 2       audio   AMR, 78.240 secs, 8 kbps, 8000 Hz
> > > 3       hint    Payload H263-2000 for track 1
> > > 4       hint    Payload AMR for track 2
> > >
> > > The audio does sound correct when played back on a pc.
> > > I also tried with lower bitrates for both audio and video but without
> > > result.
> > >
> > > Any clues in what I'm doing wrong?
> > > Thanks in advance.
> > >
> > > René
> > >
> > > -----Oorspronkelijk bericht-----
> > > Van: asterisk-video-bounces at lists.digium.com
> > > [mailto:asterisk-video-bounces at lists.digium.com] Namens Sergio Garcia
> > > Murillo
> > > Verzonden: donderdag 5 april 2007 12:48
> > > Aan: Development discussion of video media support in Asterisk
> > > Onderwerp: Re: [Asterisk-video] aac audio
> > >
> > > Hi
> > >
> > > Why do you need to use AAC?
> > > You should use one of the codecs supported by asterisk, currently you
> can
> > > use pmcu or gsm-amr (for using it with app_h324m).
> > > I added an application a few days ago for creating an mpr4 file from a
> > pcmu
> > > file, you can find it here:
> > >
> > > http://sip.fontventa.com/svn/asterisk/tools/pcm2mp4.cpp
> > >
> > > Greetings
> > > Sergio
> > >
> > > ----- Original Message ----- 
> > > From: "René van Weert" <rvweert at gmail.com>
> > > To: "'Development discussion of video media support in Asterisk'"
> > > <asterisk-video at lists.digium.com>
> > > Sent: Thursday, April 05, 2007 12:17 AM
> > > Subject: [Asterisk-video] aac audio
> > >
> > >
> > > Hi everyone,
> > >
> > > I'm using app_mp4 right now and it is working great. The only problem I
> > have
> > > is that I cannot generate 8000hz AAC audio with my ffmpeg. I tried also
> > > several different (precompiled) versions but without any luck. Ffmpeg
> only
> > > accepts 11025hz or higher. Is there any other way to create the audio
> for
> > > the mp4 file?
> > >
> > > With kind regards,
> > >
> > > René van Weert
> > >
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> -- 
> Francesco Emmi
> A-Tono
> Largo Paisiello, 5 - 95124 Catania
> Tel.: (+39) 095.7365312
> http: www.a-tono.com
> 
> 
> 
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-- 
Francesco Emmi  
A-Tono
Largo Paisiello, 5 - 95124 Catania
Tel.: (+39) 095.7365312
http: www.a-tono.com
 
 
 
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