Choppy audio playing a videofile through webrtcsink

Tue Nov 28 14:24:41 UTC 2023

No that was what I meant indeed, you might simply be running out of CPU
cycles, what's the behavior with audio only?

On Mon, 2023-11-27 at 23:34 +0100, Vincent Deconinck via gstreamer-
devel wrote:
> Hi Mathieu,
> 
> Thanks again for your replies.
> As uridecodebin already includes queues (if I read correctly), I
> tried adding A/V queues (with default values) at the end, as follows
> : 
> +--------------------------------------------------------------------
> -------------------+
> | uridecodebin.audio ->- audioconvert ->- audioresample ->- queue ->-
>  webrtcssink.audio |
> | uridecodebin.video ----->----- videoconvert ------>------ queue ->-
>  webrtcssink.video |
> +--------------------------------------------------------------------
> -------------------+
> But unfortunately it did not bring any audible improvement.
> I also tried adding another one between converting and resampling
> audio, as follows:
> +--------------------------------------------------------------------
> -----------------------------+
> | uridecodebin.audio ->- audioconvert ->- queue ->- audioresample ->-
> queue ->- webrtcssink.audio |
> | uridecodebin.video -------->-------- videoconvert -------->--------
>  queue ->- webrtcssink.video |
> +--------------------------------------------------------------------
> -----------------------------+
> To no avail :-(
> 
> But maybe that wasn't what you meant ?
> 
> KR, 
> 
> Vincent
> 
> On Mon, Nov 20, 2023 at 3:05 PM Mathieu Duponchelle
> <mathieu at centricular.com> wrote:
> > Have you tried using queues to smooth things out between the
> > uridecodebin and webrtcsink?
> > 
> > On Fri, 2023-11-17 at 01:13 +0100, Vincent Deconinck via gstreamer-
> > devel wrote:
> > > Hi,
> > > 
> > > Thanks for all the insightful answers. The log suggestion and the
> > > audio frame timing issue triggered the idea of a few more tests.
> > > 
> > > Here are the tests I did today:
> > > 1. (set logging with GST_DEBUG=5). Ran the gstreamer server and
> > > the
> > > browser with "choppy audio". The log is 350+MB and file writing
> > > clearly impacts the playback (audio choppiness is increased and
> > > video
> > > becomes choppy too). AFAICT however, the log shows no ERROR until
> > > the
> > > end of the video ("pause task, reason: Flushing"). The zipped log
> > > is
> > > available on https://we.tl/t-n3kLKluEXE
> > > 2. (still logging with GST_DEBUG=5) Changed the pipeline to only
> > > use
> > > the audio from the webm trailer video file, and used a
> > > videotestsrc
> > > as the video source => audio is still very choppy
> > > 3. (still logging with GST_DEBUG=5) Extracted the audio to a
> > > plain
> > > uncompressed wav file (obtained with "ffmpeg -i sintel_trailer-
> > > 480p.webm sintel_trailer-480p.wav") and used this as the audio
> > > source
> > > and the videotestsrc as the video source => audio is still very
> > > choppy
> > > 4. (no logging from here on) Same test: WAV file as the audio
> > > source
> > > and the videotestsrc as the video source => audio is perfect !
> > > 5. Back to using the webm file as the audio source and the
> > > videotestsrc as the video source => audio is choppy
> > > 6. Converted the source file (vp8+vorbis) to mpeg4 (h264+aac)
> > > with
> > > "ffmpeg -i sintel_trailer-480p.webm sintel_trailer-480p.mp4" and
> > > used
> > > this as the audio source and the videotestsrc as the video source
> > > =>
> > > audio is "almost" perfect (I can still hear a "drop" in the
> > > second
> > > drum at 00:16, which is not present when playing the mp4 file
> > > locally
> > > with VLC).
> > > 7. Used the mp4 as source for both video and audio => Fails with
> > > "Error received from element wsink: There is no codec present
> > > that
> > > can handle the stream's type.". Seems h264 video is not
> > > recognized ?
> > > 8. Converted the source file (vp8+vorbis) to a ts
> > > (mpeg2video+ac3)
> > > with "ffmpeg -i sintel_trailer-480p.webm -acodec ac3 -vcodec
> > > mpeg2video sintel_trailer-480p.ts" and used it for both video and
> > > audio => Fails with "There is no codec present that can handle
> > > the
> > > stream's type". Seems mpeg2video is also not recognized ?
> > > 9. Baked an alternate webm file using opus instead of vorbis with
> > > "ffmpeg -i sintel_trailer-480p.webm -strict -2 -acodec opus -
> > > vcodec
> > > copy sintel_trailer-480p_opus.webm" => audio/video is perfect !
> > > 
> > > OK. What did I learn ?
> > > - a lack of resources (e.g. heavy logging) causes choppiness. My
> > > PC
> > > is quite good though (core i9 3.6GHz 32GB w/ GeForce RTX 2060)
> > > but
> > > maybe logging chokes gsteamer.
> > > Regarding audio codecs :
> > > - Vorbis causes atrocious choppiness.
> > > - AAC is almost OK
> > > - Wav and Opus are perfect
> > > Regarding video codecs:
> > > - It seems this pipeline only accepts vp8 as input
> > > 
> > > Questions: 
> > > My source files being either mpeg4 (with aac or ac3 audio) or
> > > even
> > > MXF (and conversion beforehand not being an option),
> > > - How can I convert the videos on the fly ? 
> > > - Isn't vconvert meant to perform the conversion if required ?
> > > 
> > > Sorry again for the newbie questions...
> > > 
> > > Kind regards,
> > > 
> > > Vincent
> > > 
> > > On Thu, Nov 16, 2023 at 7:07 PM cfd new <newcfd at yahoo.com> wrote:
> > > >  
> > > > Thank you so much for your detailed mail. Very nice!
> > > > 
> > > >     Joe
> > > > 
> > > >  
> > > >  
> > > >  
> > > >  On Thursday, November 16, 2023, 01:00:44 p.m. EST, cfd new via
> > > > gstreamer-devel <gstreamer-devel at lists.freedesktop.org> wrote: 
> > > >  
> > > > 
> > > >  
> > > > 
> > > >  
> > > >  
> > > > Hi, Philipp, 
> > > > 
> > > >    very interested in your code. I got the following message
> > > > when I
> > > > stream a live video to youtube. Maybe it is related to your
> > > > case.
> > > > 
> > > >    Joe
> > > > 0:03:35.140304346 21323 0x7f1fa004c240 WARN         
> > > >  audioresample
> > > > gstaudioresample.c:732:gst_audio_resample_check_discont:<audior
> > > > esam
> > > > ple1> encountered timestamp discontinuity of 639 samples =
> > > > 0:00:00.039937500
> > > > 0:03:35.141001930 21323 0x7f1fa004c240 WARN         
> > > >  audioresample
> > > > gstaudioresample.c:732:gst_audio_resample_check_discont:<audior
> > > > esam
> > > > ple1> encountered timestamp discontinuity of 639 samples =
> > > > 0:00:00.039937500
> > > > 0:03:35.141314636 21323 0x7f1fa004c240 WARN         
> > > >  audioresample
> > > > gstaudioresample.c:732:gst_audio_resample_check_discont:<audior
> > > > esam
> > > > ple1> encountered timestamp discontinuity of 639 samples =
> > > > 0:00:00.039937500
> > > > 
> > > >  
> > > >  
> > > >  
> > > >  On Thursday, November 16, 2023, 06:35:55 a.m. EST, Philipp B
> > > > via
> > > > gstreamer-devel <gstreamer-devel at lists.freedesktop.org> wrote: 
> > > >  
> > > > 
> > > >  
> > > > 
> > > >  
> > > > Hi,
> > > > 
> > > > [dislaimer: I didnt work with gstreamer for some time, my
> > > > terminology
> > > > might be a bit rusty]
> > > > 
> > > > I also had audio issues when streaming video files over webrtc,
> > > > and
> > > > judging by your video, it could be the same issue you face.
> > > > 
> > > > For me it turned out to be small rounding errors in the audio
> > > > frame
> > > > timestamps. Due to the realtime nature, browsers playing webrtc
> > > > audio
> > > > are not aiming for a perfect smooth playback, but rather for
> > > > perfect
> > > > realtime. Small deviations in timestamps instantly lead to the
> > > > browser
> > > > inserting small pieces of silence, or dropping a few ms of
> > > > audio.
> > > > 
> > > > The most obvious effect was the volume being way lower than it
> > > > should
> > > > be. This was caused by the player/browser constantly fading
> > > > segments
> > > > in and out, to overlap them with the next one, or with silence.
> > > > Also,
> > > > I had similar distortion artifacts than you have.
> > > > 
> > > > To be clear, my issue seemed to be related to transmission of
> > > > non-live, pre-encoded video only. WebRTC is made for live
> > > > transmissions, where audio frame timestamps are directly
> > > > related to
> > > > the wall clock time at which a segment has been recorded. In
> > > > contrast,
> > > > a non-live video file typically has a stream of audio segments,
> > > > which
> > > > are expected to be played back without gaps, even when there
> > > > are
> > > > small
> > > > gaps according to the time stamps.
> > > > 
> > > > What happens if you increase the audio frame size? In my case,
> > > > this
> > > > was improving the situation dramatically, but not fully fixing
> > > > it.
> > > > 
> > > > In the end, I got this solved by "smoothing" audio time stamps.
> > > > I
> > > > wrote my own gstreamer element, that kept an estimation of the
> > > > next
> > > > frames timestamp, based on the last frame. In case, there is a
> > > > small
> > > > deviation (e.g. below 5 ms), the frames timestamp will be
> > > > changed
> > > > to
> > > > that of the estimation. I can provide the code of that element
> > > > in
> > > > case
> > > > your interested.
> > > > 
> > > > Philipp
> > > > 
> > > > Am Mi., 15. Nov. 2023 um 23:39 Uhr schrieb Vincent Deconinck
> > > > via
> > > > gstreamer-devel <gstreamer-devel at lists.freedesktop.org>:
> > > > 
> > > > > 
> > > > > Hi,
> > > > > 
> > > > > I made some progress in my quest to stream video files to a
> > > > > browser using webrtcssink, but audio is not OK. I built the
> > > > > following pipeline:
> > > > > +------------------------------------------------------------
> > > > > ----
> > > > > -------------+
> > > > > | uridecodebin.audio ->- audioconvert ->- audioresample ->-
> > > > > webrtcssink.audio |
> > > > > | uridecodebin.video ----->----- videoconvert ------>------
> > > > > webrtcssink.video |
> > > > > +------------------------------------------------------------
> > > > > ----
> > > > > -------------+
> > > > > 
> > > > > The webrtcsink pads are statically linked, and the
> > > > > uridecodebin
> > > > > pads are dynamically linked upon "pad_added" signal (as in
> > > > > https://gstreamer.freedesktop.org/documentation/tutorials/basic/dynamic-pipelines.html
> > > > > ).
> > > > > 
> > > > > Problem: The video looks OK in the browser, but the audio is
> > > > > choppy. A quick and dirty (sorry) video tells a thousand
> > > > > words:
> > > > > https://youtu.be/1EbPHLZvVLc?t=27
> > > > > 
> > > > > (using signalling server, JS API and gstreamer built 2 days
> > > > > ago
> > > > > from git HEAD)
> > > > > 
> > > > > I was first using the http URI to the source video but I also
> > > > > tried using a local copy of the file, to no avail.
> > > > > 
> > > > > Any idea what could be wrong ? Or an idea how I could track
> > > > > down
> > > > > that issue ?
> > > > > 
> > > > > Kind regards,
> > > > > 
> > > > > Vincent
> > > >  
> > > >  
> > > >  
> > > >  