Re: [Opalvoip-user] Sending a video with audio to remote

[Robert J. <ro...@vo...>]

I suppose you could. Though there is a couple of RFC's on the "official" 
manner for setting up A/V linkage for lip sync. Including things like 
getting the skew between the audio and video.

And hardly anyone does lip sync in videotelephony calls. It's a 
difficult problem and has limited gain in quality so everyone pretty 
much does everything in real time. So, it is not really necessary for 
the transmit side.

*Robert Jongbloed*
/OPAL/OpenH323/PTLib Architect and Co-founder./
Commercial support at http://www.voxlucida.com.au

On 30/10/2013 3:14 PM, JD Rosensweig wrote:
> Thanks Robert.
>
> Okay that's fine.  So there would be an Audio and Video input device 
> which would both read from the mp4 file.  Is it possible within the 
> existing infrastructure to synchronize them via the CNAME?    I guess 
> more broadly do the independent input device suffer from the same 
> deficiencies that you mentioned?
>
> From: Robert Jongbloed <ro...@vo... 
> <mailto:ro...@vo...>>
> Organization: Vox Lucida Pty. Ltd.
> Reply-To: "ro...@vo... <mailto:ro...@vo...>" 
> <ro...@vo... <mailto:ro...@vo...>>
> Date: Tuesday, October 29, 2013 9:00 PM
> To: "opa...@li... 
> <mailto:opa...@li...>" 
> <opa...@li... 
> <mailto:opa...@li...>>
> Subject: Re: [Opalvoip-user] Sending a video with audio to remote
>
> Craig and I have discussed this on a number of occasions. There are 
> very good reasons for having such a concept (A/V rather than just A or 
> just V) the main ones being lip sync, and the fact that if you are 
> writing to an MP4 file, then it can't be done by two sub-systems 
> simultaneously. Unfortunately, as usual, the primary problem is the 
> time to consider a good API and develop it. It is not a simple task, 
> and both the PSoundChannel interface and the PVideoDevice interface 
> have deficiencies: codecs, bit rate control, Intra Frame requests, 
> timestamps, synchronisation are but a few.
>
> For A/V transmission, there should be no problem in opening the MP4 
> file twice, read only, and sending through the existing interfaces.
>
>
> *Robert Jongbloed*
> /OPAL/OpenH323/PTLib Architect and Co-founder./
> Commercial support at http://www.voxlucida.com.au
>
> On 30/10/2013 2:48 PM, JD Rosensweig wrote:
>> Will this still be separate Input devices or does it make more sense 
>> to do a PAudioVideoInputDevice which can read one mp4 file and 
>> provide two streams?
>>
>> From: Robert Jongbloed <ro...@vo... 
>> <mailto:ro...@vo...>>
>> Organization: Vox Lucida Pty. Ltd.
>> Reply-To: "ro...@vo... 
>> <mailto:ro...@vo...>" <ro...@vo... 
>> <mailto:ro...@vo...>>
>> Date: Tuesday, October 29, 2013 8:25 PM
>> To: "opa...@li... 
>> <mailto:opa...@li...>" 
>> <opa...@li... 
>> <mailto:opa...@li...>>
>> Subject: Re: [Opalvoip-user] Sending a video with audio to remote
>>
>> I am afraid you will have to implement a PSoundChannel that takes the 
>> .mp4 file and provides PCM-16. A sort of high speed collision between 
>> the WAV file player in pwavfiledev.cxx and the FFMPEG video stuff in 
>> pffvdev.cxx.
>>
>> Sorry.
>>
>> *Robert Jongbloed*
>> /OPAL/OpenH323/PTLib Architect and Co-founder./
>> Commercial support at http://www.voxlucida.com.au
>>
>> On 26/10/2013 10:23 AM, Toan Vuong wrote:
>>> Hi all,
>>> I'm trying to make my application send a video with audio (*.mp4) to 
>>> a remote endpoint in a one-to-one call. I'm starting off with 
>>> simpleopal in Eridani trunk.
>>>
>>> I noticed the --grabber option, which can send an avi. I also 
>>> followed it to pffvdev.h, and modified the DefaultAVIFileName 
>>> variable to "*.mp4" instead of "*.avi". Since this just uses ffmpeg 
>>> in the background, I thought this might work. This doesn't seem to 
>>> be the best way, however.
>>>
>>> That's all fine and dandy and I can use --grabber myvideo.mp4 to 
>>> send video.
>>>
>>> How do I send audio along with it? I've extracted the audio from my 
>>> *.mp4, and used --sound-in myvideo.wav to send an audio file along, 
>>> which works. But using this method I would have to manually get the 
>>> sound from the video. It looks like I could potentially create a new 
>>> sound device to play *.mp4 files via ffmpeg, but is there a built-in 
>>> mechanism for playing audio and video in sync? Using ffmpeg twice, 
>>> once to play audio and once to play video doesn't seem like a very 
>>> efficient method to do this.
>>>
>>> Thanks,
>>> Toan
>>>
>>>
>>>
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