[Bug 759141] New: Audio/video performance regression 1.4.5 -> 1.6.1

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=759141

            Bug ID: 759141
           Summary: Audio/video performance regression 1.4.5 -> 1.6.1
    Classification: Platform
           Product: GStreamer
           Version: 1.6.1
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: gstreamer (core)
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: bjorn.forsman at gmail.com
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

Hi,

While updating GStreamer from 1.4.5 to 1.6.1 in NixOS, I found that video
recording performance regressed quite a bit (lots of dropped audio samples).

I initially found this in Cheese (webcam app), but it was easily reproducible
on the command line. In 1.4.5 I could capture just fine at 1280x720, but with
1.6.1 I have to stay at 640x480 or lower to prevent dropped audio samples:

$ gst-launch-1.0 -e webmmux name=mux ! filesink location=test.webm v4l2src !
video/x-raw,width=1280,height=720 ! videoconvert ! vp8enc ! queue ! mux.
autoaudiosrc ! audio/x-raw,rate=44100 ! vorbisenc ! queue ! mux.
Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Setting pipeline to PLAYING ...
New clock: GstPulseSrcClock
Redistribute latency...
Redistribute latency...
WARNING: from element
/GstPipeline:pipeline0/GstAutoAudioSrc:autoaudiosrc0/GstPulseSrc:autoaudiosrc0-actual-src-puls:
Can't record audio fast enough
Additional debug info:
gstaudiobasesrc.c(866): gst_audio_base_src_create ():
/GstPipeline:pipeline0/GstAutoAudioSrc:autoaudiosrc0/GstPulseSrc:autoaudiosrc0-actual-src-puls:
Dropped 26019 samples. This is most likely because downstream can't keep up and
is consuming samples too slowly.

The video has so much dropped audio that it's completely useless. (Maybe ~50
percent of the real time audio gets recorded?)

If you have the Nix package manager, you can reproduce by checking out
https://github.com/NixOS/nixpkgs/pull/11491 and running

$ timeout -s INT 30s nix-shell -p gst_all_1.gstreamer
gst_all_1.gst-plugins-base gst_all_1.gst-plugins-good gst_all_1.gst-plugins-bad
gst_all_1.gst-plugins-ugly less time -I nixpkgs=. --run "\time gst-launch-1.0
-e webmmux name=mux ! filesink location=test.webm v4l2src !
video/x-raw,width=1280,height=720 ! videoconvert ! vp8enc ! queue ! mux.
autoaudiosrc ! audio/x-raw,rate=44100 ! vorbisenc ! queue ! mux."

(Then switch back to HEAD~4 to get back to gstreamer 1.4.5 and see the
difference.)

My system is Intel i7-5500U CPU @ 2.40GHz with 8 GiB RAM (laptop).

Best regards,
Bjørn Forsman

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