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

[GStreamer (GNOME Bugzilla)]

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

--- Comment #7 from bjorn.forsman at gmail.com ---
I looked up the gstreamer source code and found that the default value for
"deadline" in vp8enc is 0 (by macro expansion), and it comes from
https://github.com/webmproject/libvpx/blob/master/vpx/vpx_encoder.h#L898-L903,
pasted below:

#define VPX_DL_REALTIME     (1)        /**< deadline parameter analogous to
  *   VPx REALTIME mode. */
#define VPX_DL_GOOD_QUALITY (1000000)  /**< deadline parameter analogous to
  *   VPx GOOD QUALITY mode. */
#define VPX_DL_BEST_QUALITY (0)        /**< deadline parameter analogous to
  *   VPx BEST QUALITY mode. */

So it selects "best quality" by default. I tried with "good quality" mode, but
that too drops audio. No wonder, as it is 1000000x longer deadline than the
"realtime" mode :-)

I don't know what is worse, dropping audio in recording scenarios or having
less than best quality when doing offline / non-realtime transcoding (or
whatnot)? Well, I'm a bit biased now because I hit this issue, so I guess I'd
prefer the realtime mode by default. But I appreciate that it's not a simple
choice to make. And either way, Cheese should really specify "vp8enc
deadline=1" in its pipeline.

I think I'll suggest that NixOS switches gstreamer from 1.4.5 to 1.6.1 now.

Thanks for your help, Nicolas.

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