[linux-dvb] Re: SAA7146_MAX_BUF limit

[Peter Maersk-Moller <peter@maersk-moller.net>]

Hi Douglas

Douglas Kosovic wrote:
> 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

The best I get is this
1       video   MPEG-4 Simple @ L3, 19.840 secs, 934 kbps, 352x288 @ 19.61 fps
2       audio   MPEG-4, 16.783 secs, 125 kbps, 44100 Hz

If I switch to MP3 I can get this
1       video   MPEG-4 Simple @ L3, 19.840 secs, 1203 kbps, 352x288 @ 25.00 fps
2       audio   MPEG-2 (MP3), 19.827 secs, 127 kbps, 44100 Hz

In both cases BW for wideo was set to 1000kbps.

AAC is a CPU hog. I'm running headless but X is running. Again
my CPU is a single Athlon XP1800+. I haven't tried overclocking yet.

So in the 352x288 case, the limiting factor is the CPU, not the DVB card.

> 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) ?

Yes. It is with mp4live. I also tried with xawtv. With mp4live
I get

1       video   MPEG-4 Simple @ L3, 19.760 secs, 860 kbps, 720x576 @ 16.35 fps
2       audio   MPEG-2 (MP3), 19.852 secs, 126 kbps, 44100 Hz

And at all times (until hinting afterwards) I have at least 10% idle
capacity on the CPU. So here the limiting factor is not the CPU but
rather the DVB card.

If I use xawtv, I get into trouble trying to do more than 3-5 fps
for 704x576.

> >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.

Changing from 2 to 4 or 5 made only a little (but noticable difference to
the better. 5 and not 4 is the maximum.

Changing SAA7146_MAX_BUF to 15 made my computer a bit Windows like (it crashed).

--PMM


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