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
>
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