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@xxxxxxxxxxxxxxx>
> ---
> 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
> ];
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