[Bug 763011] New: avfvideosrc: h264 support, optimize latency

GStreamer (GNOME Bugzilla) bugzilla at gnome.org
Wed Mar 2 20:52:56 UTC 2016


https://bugzilla.gnome.org/show_bug.cgi?id=763011

            Bug ID: 763011
           Summary: avfvideosrc: h264 support, optimize latency
    Classification: Platform
           Product: GStreamer
           Version: git master
                OS: Mac OS
            Status: NEW
          Severity: enhancement
          Priority: Normal
         Component: gst-plugins-bad
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: jhgorse at gmail.com
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

I would like to add h264 output support to the avfvidesrc element (i.e. the
AVFoundation Session within it) in order to improve the encode/decode latency.
When using vtenc_h264 and vtdec_hw, the total pipeline latency is increased 200
ms (~6 frames). I am still new to how GStreamer manages buffers and all this,
though in a direct application using native API's I'd expect 2-4 frames of
additional latency for h.264 encoding and decoding for real-time streaming.

The following pipelines were used for these measurements:

# With vtenc/vtdec and realtime settings
gst-launch-1.0 avfvideosrc device-index=0 !
"video/x-raw(memory:GLMemory),width=1280,height=720" ! gldownload qos=true !
vtenc_h264 realtime=true allow-frame-reordering=false ! vtdec_hw ! glimagesink

latency = 366 ms

# Without vtenc/vtdec
gst-launch-1.0 avfvideosrc device-index=0 !
"video/x-raw(memory:GLMemory),width=1280,height=720" ! glimagesink

latency = 166 ms

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