[mythtv] Ticket #7964: Predictively skip frames to smooth out timestretch

[John P Poet]

On Mon, May 10, 2010 at 9:14 AM, David Engel <david at istwok.net> wrote:
> On Mon, May 10, 2010 at 08:00:15AM +1000, Mark Spieth wrote:
>> >Are there any known reasons why your patch won't work with 0.23-fixes,
>> >other than having to manually apply some parts?  v5 worked fine on
>> >1080i, and on 720p at normal speed.  It didn't work very well on 720p,
>> >however, when timestretch was used.  After a skip, the video would
>> >stop updating and it could never resync until timestretch was turned
>> >off.
>> >
>> not that I know of.
>> what is your refresh rate and source frame rate and vsync mode?
>> vdpau or not? 6 ch or 2 ch or digitalout?
>
> This was with an atsc mpeg2 1280x720x60 (really 59.94 fps) recording
> played on a 1920x1080x60 display using vdpau and rtc timing.  The
> audio was 2-channel AC3 played over HDMI.
>
>> I suspect frameinterval < refreshinterval for your case and I wasnt
>> able to test that scenario. john tested and apparently was ok.
>> have you tested on trunk? if so can you provide a small segment of
>> such a recording?
>> or if it works ok on trunk then you will have to run with
>> playback,audio,timestamp with a couple of extra logs enabled in
>> AVSync (#if) and vsync.cpp (#define GLVSYNCDEBUG) and do a short run
>> and send me the logs.
>
> OK.  It'll be at least tomorrow before I can do any more testing.
>
>
> On Sun, May 09, 2010 at 04:08:25PM -0600, John P Poet wrote:
>> I finally upgrading to version 5 of Mark's patch and also notice that
>> skipping around in a video causes issues.  General playback (with
>> timestretch) is fine, but it can take several seconds for playback to
>> become smooth again after a skip -- If there is a ticker-tape on the
>> screen, it will be a bit jerky for a few seconds before smoothing out
>> again.
>
> That sounds like the same problem.

After a jump, how long it takes for the audio and video to get back in
sync can vary a lot.  Sometimes it syncs back up almost instantly, but
other times it can take over 5 seconds.  When it takes a while, it is
very distracting -- especially if someone is talking and their lips
have nothing to do with what they are saying ;-)

Mark, I think this patch is the right direction, but I am hoping the
A/V sync can be improved.


Thanks,

John
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