Gapless Playback with Playbin

[David Harks]

Luis,

https://www.dropbox.com/sh/es6nekvhcexh7xl/AACeOiu9F_OrNgTuUzr-gJyja

I've created a test case that clearly demonstrates the issue. Here's the
play command line I used:

GST_DEBUG=*:4 gst-play-1.0 --videosink xvimagesink --gapless Part_one.mp4
Part_two.mp4 Part_three.mp4 > Gapless.out 2>&1

At the above link is the result (Gapless.out) as well as the three MP4
files used for the demonstration. The files were generated by creating 300
frames of PNGs, with the frame number placed at (frame, frame) coordinate
in the image, in white text; these were then encoded to H.264 and played
back. The numbering and movement make the gaps very obvious!

Using VLC to play these three files results in a continuous stream, but
gst-play has a 5-10 frame pause at approximately the point where
"about-to-finish" is emitted.

Thanks for your help!

-d


On Mon, Jul 14, 2014 at 4:36 PM, Luis de Bethencourt <luis at debethencourt.com
> wrote:

> Seeing that duration before a real value is discovered by the demuxer is
> normal. But those FIXME lines do look scary.
>
> Will read your log in a while.
>
> Thanks,
> Luis
>
>
> On 14 July 2014 13:43, David W. Harks <dave at dwink.net> wrote:
>
>> Sure, here you go, at debug level 4.
>>
>> https://www.dropbox.com/s/cdh1ur7vsmt6q5m/dbg_4.log
>>
>> One thing I noticed: the segment start events go like this, with a
>> duration of 99:99:99 and then complaints about duration caching:
>>
>> creating segment event time segment start=0:00:00.066733333, stop=0:00:
>> 14.347666666, rate=1.000000, applied_rate=1.000000, flags=0x00,
>> time=0:00:00.000000000, base=0:00:00.000000000, position 0:00:00.066733333,
>> duration 99:99:99.999999999
>> 0:00:00.675879247 14212      0x1f99a00 FIXME                    bin
>> gstbin.c:4008:gst_bin_query: implement duration caching in GstBin again
>> 0:00:00.675908879 14212      0x1f99a00 FIXME                    bin
>> gstbin.c:4008:gst_bin_query: implement duration caching in GstBin again
>> 0:00:00.675919229 14212      0x1f99a00 FIXME                    bin
>> gstbin.c:4008:gst_bin_query: implement duration caching in GstBin again
>>
>> I'm not sure if that has much to do with what I'm seeing, but it would
>> mean the segment starts on the third frame(at apprximately 30fps).
>>
>> Thanks in advance for looking!
>>
>> -d
>>
>>
>>
>> On Mon, Jul 14, 2014 at 11:35:09AM -0400, Luis de Bethencourt wrote:
>>
>>> Hi David,
>>>
>>> Can you generate the log again with a lower debug level? Your current log
>>> is 100mb big and very very long. Would be easier to debug with a lower
>>> debug level.
>>>
>>> Thanks,
>>> Luis
>>>
>>>
>>> On 11 July 2014 08:35, David W. Harks <dave at dwink.net> wrote:
>>>
>>>  GStreamer wizards,
>>>>
>>>> My GStreamer-based app is intended to play H.264 video clips
>>>> back-to-back
>>>> in gapless fashion. It uses playbin and the 'about-to-finish' signal to
>>>> change URIs, as the various examples and advice about this shows.
>>>>
>>>> Unfortunately, I'm seeing a 5-10 frame 'pause' when switching URIs. What
>>>> seems to be happening is that the sink stops rendering frames for a
>>>> brief
>>>> period, leaving a static frame visible, then 'catches up' and starts
>>>> rendering again, skipping the first few frames of the next clip. I tried
>>>> taking the same clips and playing them with gst-play-1.0 --gapless and I
>>>> get the same result.
>>>>
>>>> My question is, how can I narrow down what's going on here? And is there
>>>> anything I can do to get frame-perfect transitions? I created a debug
>>>> log
>>>> with GST_DEBUG=5 here: https://www.dropbox.com/s/
>>>> 0rdzlrcaz77wbkc/dbg.out.gz
>>>>
>>>> Unfortunately, I'm not quite sure how to interpret this output.
>>>>
>>>> Thanks for your expertise!
>>>>
>>>> -d
>>>> _______________________________________________
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>>>> gstreamer-devel at lists.freedesktop.org
>>>> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>>>>
>>>>
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>
>
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>


-- 
d.w. harks <dave at dwink.net>
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