[Spice-devel] [PATCH spice-html5] Review the webm audio track header and remove the fixmes.

[Frediano Ziglio]

Hi,
  why this was not merged ?

Frediano

> 
> Ack
> 
> Thanks,
> Pavel
> 
> On Fri, 2016-12-23 at 10:53 -0600, Jeremy White wrote:
> > This involved a review of the Firefox parsing code along
> > with the official specifcation, and setting these fields
> > to the specified default values.
> > 
> > Most notably, I have found that recent browsers do not need the
> > 8 ms pre skip, and it seems to remove some audio lag to
> > switch to 0.
> > 
> > Signed-off-by: Jeremy White <jwhite at codeweavers.com>
> > ---
> >  webm.js | 27 +++++++++++++++++++--------
> >  1 file changed, 19 insertions(+), 8 deletions(-)
> > 
> > diff --git a/webm.js b/webm.js
> > index 789da14..72c1853 100644
> > --- a/webm.js
> > +++ b/webm.js
> > @@ -393,28 +393,39 @@ webm_SeekHead.prototype =
> >  
> >  function webm_AudioTrackEntry()
> >  {
> > +    /*
> > +    ** In general, we follow this specification:
> > +    **   https://www.matroska.org/technical/specs/index.html
> > +    ** we supply the mandatory values, and a comment notes
> > +    ** where we differ from the default
> > +    **   There is one RECOMMENDED guideline we are omitting;
> > +    ** the OPUS codec_delay is recommended to be 80ms.
> > +    ** However, the spice server does not currently provide time
> > +    ** stamps that are offset by 80ms, so you effectively get an
> > +    ** 80ms lag with this setting.
> > +    */
> >      this.id = WEBM_TRACK_ENTRY;
> >      this.number = 1;
> >      this.uid = 1;
> >      this.type = 2; // Audio
> >      this.flag_enabled = 1;
> >      this.flag_default = 1;
> > -    this.flag_forced = 1;
> > -    this.flag_lacing = 0;
> > -    this.min_cache = 0; // fixme - check
> > +    this.flag_forced = 1;  // Different than default; we wish to
> > force
> > +    this.flag_lacing = 1;
> > +    this.min_cache = 0;
> >      this.max_block_addition_id = 0;
> > -    this.codec_decode_all = 0; // fixme - check
> > -    this.seek_pre_roll = 0; // 80000000; // fixme - check
> > -    this.codec_delay =   80000000; // Must match
> > codec_private.preskip
> > +    this.seek_pre_roll = 0;
> > +    this.codec_delay =   0; // Must match codec_private.preskip
> >      this.codec_id = "A_OPUS";
> > +    this.codec_decode_all = 1;
> >      this.audio = new webm_Audio(OPUS_FREQUENCY);
> >  
> >      // See:  http://tools.ietf.org/html/draft-terriberry-oggopus-01
> >      this.codec_private = [ 0x4f, 0x70, 0x75, 0x73, 0x48, 0x65,
> > 0x61, 0x64,  // OpusHead
> >                             0x01, // Version
> >                             OPUS_CHANNELS,
> > -                           0x00, 0x0F, // Preskip - 3840 samples -
> > should be 8ms at 48kHz
> > -                           0x80, 0xbb, 0x00, 0x00,  // 48000
> > +                           0x00, 0x00, // Preskip - 3840 samples
> > would be 8ms at 48kHz
> > +                           0x80, 0xbb, 0x00, 0x00,  // nominal rate
> > - 48000
> >                             0x00, 0x00, // Output gain
> >                             0x00  // Channel mapping family
> >                             ];