[linux-dvb] Tuning problems with TT DVB-C 1500 (saa7146 + stv0297) and QAM128

Ville Vehvilainen vvehvilainen at gmail.com
Fri Aug 12 11:04:59 CEST 2005


On 8/11/05, Simo Kivimäki <simo at kivimaki.name> wrote:
> > ~> czap -r -c channels.conf MTV3
> > using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
> > reading channels from file '.mplayer/channels.conf'
> >  15 MTV3:346000000:INVERSION_AUTO:6900000:FEC_NONE:QAM_128:305:561:49
> >  15 MTV3: f 346000000, s 6900000, i 2, fec 0, qam 4, v 0x131, a 0x231
> > status 1f | signal 033a | snr 0ee2 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> > status 1f | signal 0339 | snr 0dea | ber 00000000 | unc 00000000 | FE_HAS_LOCK
>
> I get about same numbers but for me the picture is perfect. Only problem
> is slow tuning. From czap command to FE_HAS_LOCK it usually takes more
> than 30 seconds. I had to increase timeouts to get it tune. How long it
> takes for you to get tuned?

It usually manages to lock in about 5 to 10 seconds. Often no lock at
all, though. The "signal" (I assume that's the signal strength) and
"snr" values look very low to me, considering that on the old card the
first is typically (always?) 0xFFFF and the second also fairly large.

Using mplayer and the old card, tuning is fast and the output as follows:

<-- snip preamble ------------->
Playing dvb://MTV3.
code taken from dvbstream for mplayer v0.4pre1 - (C) Dave Chapman 2001
Released under the GPL.
Latest version available from http://www.linuxstb.org/
dvb_tune Freq: 346000000
TS file format detected.
DEMUX OPEN, AUDIO_ID: -1, VIDEO_ID: -1, SUBTITLE_ID: -1,
PROBING UP TO 2000000, PROG: 0
VIDEO MPEG2(pid=305)...AUDIO MPA(pid=561) NO SUBS (yet)!  PROGRAM N. 0
Opened TS demuxer, audio: 50(pid 561), video: 10000002(pid 305)...POS=24064
VIDEO:  MPEG2  720x576  (aspect 2)  25.000 fps  5000.0 kbps (625.0 kbyte/s)
<-- snip rest of video/audio decoder data --------->
Starting playback...
A:54259.4 V:54259.4 A-V: -0.004 ct: -0.486  388/388   0%  0%  4.8% 0 0 0%%
(etc.)

On the new card, I just get:

<-- snip preamble --------->
Playing dvb://MTV3.
code taken from dvbstream for mplayer v0.4pre1 - (C) Dave Chapman 2001
Released under the GPL.
Latest version available from http://www.linuxstb.org/
dvb_tune Freq: 346000000
dvb_streaming_read, attempt N. 6 failed with errno 0 when reading 2048 bytes
dvb_streaming_read, attempt N. 5 failed with errno 0 when reading 2048 bytes
dvb_streaming_read, attempt N. 4 failed with errno 0 when reading 2048 bytes
dvb_streaming_read, attempt N. 3 failed with errno 0 when reading 2048 bytes
dvb_streaming_read, attempt N. 2 failed with errno 0 when reading 2048 bytes
dvb_streaming_read, attempt N. 1 failed with errno 0 when reading 2048 bytes
dvb_streaming_read, return 0 bytes
(etc.)

Using czap -r and mplayer together yields similar results.

For what it's worth, the cards are on separate, different machines,
the software is similar otherwise but the older card's in a kernel 2.4
system. I'll try to get them into the same system sometime later to
verify that's not the problem.

Ville




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