[gst-devel] Directshow sync issues

[KEVIN WEST]

> Message: 5
> Date: Sat, 15 Jan 2011 12:01:45 +0000
> From: Tim-Philipp M?ller <t.i.m at zen.co.uk>
> Subject: Re: [gst-devel] Directshow sync issues
> To: gstreamer-devel at lists.sourceforge.net
> Message-ID: <1295092905.12462.4.camel at zingle>
> Content-Type: text/plain; charset="UTF-8"
> 
> On Fri, 2011-01-14 at 19:20 -0800, KEVIN WEST wrote:
> 
>> I am running into a strange issue with a few videos and
>> dshowdecwrapper.  Basically I will transcode the video, but the output
>> is all wrong.  If you open the video, it will show the first frame
>> while playing the entire audio stream, and finally it will play the
>> video stream once it hits the end of the audio.  I thought there may
>> be some synchronization issues since dshow may not be using the same
>> clock as gstreamer, so I implemented an IReferenceClock that calls
>> into the gstreamer clock, however this doesn't seem to be fixing the
>> issue.
> 
> Clocks don't matter much in this kind of pipeline - there's neither a
> source nor a sink syncing against the clock. Timestamps on the buffers
> (and newsegment events preceding the data flow) carry the timing
> information.

Thanks for the info here Tim.  I wasn't sure it would fix the problem and it's good to know it shouldn't be necessary.

> 
>> For reference, here is my current pipeline:
>> 
>> gst-launch.exe -v --seek=0 uridecodebin name=dec uri="test.wmv" dec. !
>> videoscale ! videorate ! video/x-raw-yuv, width=320, height=240,
>> framerate=24000/1001 ! ffmpegcolorspace ! x264enc ! queue2
>> max-size-bytes=0 max-size-time=0 max-size-buffers=0 ! mux. dec. !
>> audioconvert ! audioresample ! audio/x-raw-int, rate=44100, channels=2
>> ! faac bitrate=128000 ! queue2 max-size-bytes=0 max-size-time=0
>> max-size-buffers=0 ! mux. flvmux name=mux ! filesink
>> location="output.flv"
> 
> Have you tried other muxers?

I have tried avimux, flvmux, and mpegtsmux.  With flvmux I get the playback as I described above playing in Adobe Media Player.  With avi and mpg I get either only sound or no playback in Windows Media Player.

> 
> Have you tried with other decoders? (e.g. gst-ffmpeg based)

Are you suggesting using something other than dshowdecwrapper for decoding?  I have one mov file with this synchronization issue (h264 video) when using the dshowdecwrapper, and then when using a separate plugin for decoding it works just fine.  It seems to be related to the wrapper.

> 
> Have you tried other encoders?

I have not, just x264.  This only happens for some videos, so I don't suspect the encoder, but I will give it a try and report back.

> 
> Does playback alone work?

Yes, playback in Windows Media Player of the original wmv plays fine.

> 
> Where does the --seek option come from? That's not in upstream
> gst-launch. Try without it.

Sorry, that's from custom code I have added to gst-launch.  Using the straight ossbuild version produces the same sync issue.

> 
> (Also: use a normal queue instead of queue2 here).

Haven't tried this but I'm curious about why this may work.  Shot in the dark or is there more reasoning behind it?  I'll give it a try either way.  Thanks!

> 
> Cheers
> -Tim
> 

On Jan 15, 2011, at 11:40 AM, David Hoyt wrote:

> On Fri, 2011-01-14 at 19:20 -0800, KEVIN WEST wrote:
> 
>> I am running into a strange issue with a few videos and  
>> dshowdecwrapper.  Basically I will transcode the video, but the output  
>> is all wrong.  If you open the video, it will show the first frame  
>> while playing the entire audio stream, and finally it will play the  
>> video stream once it hits the end of the audio.  I thought there may  
>> be some synchronization issues since dshow may not be using the same  
>> clock as gstreamer, so I implemented an IReferenceClock that calls  
>> into the gstreamer clock, however this doesn't seem to be fixing the  
>> issue.
> 
> Where did you get the windows build? Was it your own or via ossbuild
> (gstreamer winbuilds) or cygwin ports? And what version?
> 
> 

As far as the windows build we are using, it's based off of the ossbuild.  We have made some modifications, but I always go back and test using the original dlls as well to make sure it's not something we caused with our changes.  I believe the version is

> 
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