[linux-dvb] Re: SAA7146_MAX_BUF limit

[Douglas Kosovic <douglask@dstc.edu.au>]

Hi Peter,

>I'm having a bit of a problem with a Rev. 2.2 permium card trying
>to capture anything at a decent frame rate and a decent resolution.
>To me decent means 720x576@25fps, but I even tried 352x288@12
>which also fails. The best I can achive is 2-6fps.
>
Multicasting MPEG-4 realtime using mp4live with a Technotrend Rev 2.1 on
a dual PIII 1000, the best I can achieve is:

  video - MPEG-4 Simple @ L3, 1651 kbps, 352x288 @ 24.90 fps
  audio - MPEG-4 AAC, 128 kbps, 44100 Hz

But typically it's more closer to 19 or 20 fps, I'm fairly happy with the
quality being streamed to a Quicktime 6 client. Although when multicasting
with mp4live there is the occasional screen glitch with Quicktime 6 that
you don't see if you were playing back the same thing from a standalone
file produced by mp4live.

(note: I'm using 'mp4live --headless' and I don't have X11 running at the
time)

If I up the resolution to 720x576, the best I can achieve from mp4live is
6 fps. In your other email you say you can now capture 720x576@14fps, is
that with mp4live (MPEG4IP) ?

>I tried settings buffers=5 for saa7146-core, but that hardly
>made a difference. I also tried to change SAA7146_MAX_BUF to
>15 and setting buffers=15, but that made no difference. Is
>there a limit for SAA7146_MAX_BUF ?
>
I don't know, but the comments in saa7146_core.c state that the buffers
insmod parameter should be set to 4 (== maximum) if you plan to do 25fps
grabbing.

Doug.





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