Re: [xine-devel] reordered_timestamp_fix

[James <Ja...@su...>]

On 12/10/11 14:56, Torsten Jager wrote:
>
>
>> What stream is this trying to correct?
>> What do we need dts for? We always were fine with just pts before?
> Well, I never really was. At least not with the actual implementation.
Ok, the implementation was wrong then.
Only the PTS should be passed from demuxer to decoder in xine-lib.
That is why the parameter is called "pts".




> If there are b-frames, before decoding dts are monotonically increasing
> while pts are not. After decoding, its vice versa. Both fifos only
> support one timestamp, and I thought both need to be monotonic which
> leads to a nice conflict.
Just ignore the dts in the demuxer. Only sent pts to the decoder.
The decoder is responsible to re-ordering the pts values, so that the 
output of the decoder has monotonic pts values.

> demux_flv used to send dts (fixed locally), demux_qt still does.
> See the big comment in reordered_timestamp_fix_1b on this.
>
> demux_real was even worse, it tried to create pseudo pts out of both
> dts and pts in container (also fixed locally, any one interested?).
Ok, looks like what you are doing it correct. Using pts and not dts.
> Nobody knows the future, not even video software. Thats why reordering
> always comes along with a slight lookahead delay on both encoder and
> decoder side.
>
> Yes I know we can compensate this manually using the 'N' and 'M' keys.
> But I am editing video for use on external hardware media players who
> dont have that capability. I need correct playback for
> testing before burning on dvd.
>
>> Surely this would be better fixed by fixing the mov/mp4 video decoders
>> to output correct PTS values.
> No. This would cause a lot of second-guessing. For now, best solution
> seems to be letting demuxer send real pts (not dts).
>
> Torsten
>
Correct. Fix the sending of PTS values from demuxer to decoder.
Then, if needed, correct the decoder to output correct PTS values.

xine-lib is designed use use "Presentation Time Stamps" in order to get 
correct lip sync at the display.
xine-lib has no need for "Decoding Time Stamps". DTS values are useful 
for hardware decoders and resource restricted decoders.

Kind Regards

James