[maemo-developers] N800 & Video playback

[From: Siarhei Siamashka]

On Wednesday 02 May 2007 12:47, Daniel Stone wrote:
> > > X11 error: BadValue (integer parameter out of range for operation)
> > > MPlayer interrupted by signal 6 in module: flip_page while gstreamer
> > > did play them just fine. Also the Nokia_N800.avi and  NokiaN93.avi died
> > > in the same way.
> >
> > This X11 error on video playback start and also sometimes on switching
> > fullscreen/windowed mode is a known problem [1] reported in this mailing
> > list.
> >
> > If MPlayer dies on start, usually trying to start it again succeeds. So
> > these 320x240 and 352x288 videos could be played as well if you were a
> > bit more persistent :)
>
> Resizing is a bit tricky.  Most video hardware lets you use the hardware
> to clip, so if you move it beyond the edge of the screen, it just
> happily ignores anything beyond the hardware's bounds.  Unfortunately
> for us, attempting to move a video surface off-screen (even by just a
> few pixels) triggers a hardware lockup.
>
> Given that we can't display the frame at all, we send BadValue (there
> are a couple of other conditions where this is possible, but this is the
> main one).  I don't see the point in returning Success when no video is
> drawn at all.  So, I guess you could hack mplayer's error handler to
> just ignore BadValues from Xv(Shm)PutImage, unless you get more than
> five or ten in a row, say.

Thanks for the hint, I'll try it.

> Bear in mind that, as you've hinted at, the only part of the Xv code
> which is custom is the _output_ code.  We're using the standard X server
> implementation (as used by tens of millions of people) for the protocol
> decode and standard semantics, the standard KDrive layer for extended
> stuff (as used by god-knows-how-many embedded and consumer devices), and
> then the only part we have to play is taking frames and putting them on
> the screen.
>
> Due to some restrictions (as above), we have to deliberately error out
> on some operations.  But errors like that tend to say 'you've hit a
> hardware restriction, I can't do this', rather than 'you hit one of the
> many random return BadValues we put in this weird code just to confuse
> people'.

That's the interesting information, thanks.

> Also, bear in mind that a lot of the initial instability was due to the
> DSP.  The video was actually rather stable when you played without
> sound, although now the situation is somewhat reversed with the DSP
> being pretty steady now, and the new YUV420 code having complicated
> semsnatics.

Well, I was planning to raise this issuer later (after xserver/Xv things are
clear), but looks like DSP still has some problems on N800. In MPlayer
it can be triggered by a number of very fast sequential gstreamer pipeline
start/stop operations which usually happen on seeking. Audio playback just
hangs. Right now MPlayer artificially introduces 100ms pause to workaround
this problem. I tried to reproduce the same issue on a small test program,
but did not succeed yet.

> > I have also submitted this patch to maemo bugzilla, hopefully it (or its
> > modification) can get included into the next version of N800 firmware:
> > https://maemo.org/bugzilla/show_bug.cgi?id=1278
>
> I'll merge it with some changes.

Thanks a lot.