[ivtv-users] B-frames issue: the prove

[Alexander Pipelka]

Hans,

I reinstalled the old system.
It was Ubuntu Feisty with the ivtv driver version 0.10.0

Here the dmesg snippet:

[ 19.404000] ivtv: ==================== START INIT IVTV
====================
[   19.404000] ivtv:  version 0.10.1 (tagged release) loading
[ 19.404000] ivtv: Linux version: 2.6.20-15-generic SMP mod_unload 586
[ 19.404000] ivtv: In case of problems please include the debug info
between
[ 19.404000] ivtv: the START INIT IVTV and END INIT IVTV lines, along
with
[ 19.404000] ivtv: any module options, when mailing the ivtv-users
mailinglist.
[   19.404000] ivtv0: Autodetected Yuan MPC622 card (cx23416 based)
[ 19.404000] ivtv0: Unreasonably low latency timer, setting to 64 (was
32)
[   20.876000] ivtv0: loaded v4l-cx2341x-enc.fw firmware (262144 bytes)
[   21.104000] ivtv0: Encoder revision: 0x02050032
[   21.104000] ivtv0: Recommended firmware version is 0x02060039.
[ 21.188000] cx25840 0-0044: cx25843-23 found @ 0x88 (ivtv i2c driver
#0)
[   26.188000] ivtv0: Registered device video0 for encoder MPEG (4 MB)
[   26.188000] ivtv0: Registered device video32 for encoder YUV (2 MB)
[   26.188000] ivtv0: Registered device vbi0 for encoder VBI (1 MB)
[ 26.188000] ivtv0: Registered device video24 for encoder PCM audio (1
MB)
[   26.568000] ivtv0: Initialized Yuan MPC622, card #0
[ 26.568000] ivtv: ==================== END INIT IVTV
====================


You may believe it or not this driver produces a correct stream without
any B-Frames.

To prove my words here are two links to captured streams. One with 2
B-Frames one with 0 B-Frames.

http://www.bms-austria.com/~pipelka/2bframes.mpeg
http://www.bms-austria.com/~pipelka/0bframes.mpeg

Open them with e.g. avidemux and check the frame types.

The following commands where used to create the streams:

v4l2-ctl -i 1
v4l2-ctl -s pal

v4l2-ctl -c video_b_frames=2
cat /dev/video0 > 2bframes.mpeg

v4l2-ctl -c video_b_frames=0
cat /dev/video0 > 0bframes.mpeg


Regards,

Alex


Am Di 18.11.2008 20:57 schrieb Hans Verkuil <hverkuil at xs4all.nl>:

> On Tuesday 18 November 2008 18:13:04 Alexander Pipelka wrote:
> >  Hans,
> >
> >  The older version of the driver supported 0 B-Frames (I'm 100%
> > sure).
> >
> >  I need this for very fast frame navigation in a MPEG stream.
> >  It worked with the driver included in Ubuntu Edgy (I think it was
> > version 0.7.4 of the driver).
> >
> > Unfortunately I updated that machine to Ubuntu Hardy and the problem
> > appeared.
> >
> >  Well, I could reinstall an other machine with Ubuntu Edgy to
> > *verify* that the 0 B-Frame thing works, but I already know this,
> > ...
> >
> >  Please help !
> 
> I am not convinced. The only difference I've found between 0.7.4 and
> the
> latest driver when it comes to B-frames was corrected by my patch. As 
> far as I can tell 0.7.4 used the same firmware as well.
> 
> I vaguely remember that someone tried it with an old ivtv version as 
> well in the past and got a similar results. However, I can't find the 
> specifics so I might be wrong.
> 
> The upshot is that I *really* need to see proof that this ever worked 
> (and worked with the same firmware as well!) before I go and spend a 
> lot of time figuring out what changed. The fact that you could set 
> B-frames to 0 using ivtvctl doesn't mean at all that it actually 
> worked. Actually the value 0 that was passed to the firmware in 0.7.4 
> was not according to the fw docs since they specific that you have to 
> pass '#bframes + 1' to the firmware, so '0' should be an illegal
> value.
> 
> Regards,
> 
> 	Hans
> 
> >
> >  Alex
> >
> >  Hans Verkuil schrieb:
> > On Tuesday 18 November 2008 08:26:16 Levente Novák wrote:
> >
> > Hi,
> >
> > Is there any advance on the topic of B-frames problem on PVR-150s
> > and
> > PVR-250s? A few days ago I tested Hans' patch and while my PVR-150
> > MCE does now save a non-zero length stream if th number of B-frames
> > is set to 0, this stream has not 0 but 1 B-frames per P-frames.
> > Beside this, even if it seems to work OK with 1 or 2 B-frames, the
> > stream is choppy and unusable with 3 or 4.
> >
> >
> > My patch fixes the zero-length stream issue, but that's all. I don't
> > believe it ever gave you a stream with 0 B-frames. I suspect that
> > the
> > firmware forces a minimum of 1 B-frame.
> >
> > If you can prove that the older driver actually gave you 0 B-frames,
> > then I'll take another look. But I believe that the conclusion
> > simply
> > is that you need a minimum of 1 B-frame.
> >
> > Regards,
> >
> >         Hans
> >
> > _______________________________________________
> > ivtv-users mailing list
> > ivtv-users at ivtvdriver.org
> > http://ivtvdriver.org/mailman/listinfo/ivtv-users
> 
>