[linux-dvb] Re: DVB Newbie

[Chris Pitchford <nova-t@intrepid.cx>]

Ive got two examples of mpg files made with dvb-mplex c4 (non qam16) and
bbc1 (is qam16)

http://chris.intrepid.cx/dvbresult/

from the start the bbc1.mpg file is corrupt and noisy, the c4.mpg file
(after a few hundred meg) will become just as bad.. .but initially (as
visible in the c4.mpg file) it looks ok..

Cheers

cp

On Thu, 19 Jun 2003, Chris Pitchford wrote:

>
> I hope you dont mind me reposting to the list, Paul..
>
> I actually don't have a monitor on the that has the dvb card in it.. all
> the TV is played back across the lan. My laptop is my prefered playback
> computer, and I've not (though I REALLY should) touched mplayer or most of
> the other software on the box for a good while (6 months or so)
>
> Its not just mplayer thats causing the problem..
>
> I'm using the Crystal Palace transmitter in the UK, and I've actually just
> moved house about 1.5miles nearer, its about 3 miles from my house and I
> have a straight road to the transmitter, perfect for line of sight! :)
>
> More investigation has shown two things:
>
> Firstly, using :
>
> tzap -r CHANNEL4 &
> cat /dev/dvb/adapter0/dvr0 > c4.ts
> dvb-mplex -t MPEG2 -p 2828 -q 2827 -o c4.mpg -i TS_STREAM c4.ts
>
> will result in a good MPG file I can play with xine or mplayer.. BUT there
> are errors after a few minutes.. infact the longer I leave the "cat"
> command running, the more likely dvb-mplex will fail. Using ts2ps to play
> the ts stream into mplayer again works for a few minutes then errors
> appear and get progressively worse until mplayer dies.
>
> tzap -r "BBC ONE" &
> cat /dev/dvb/adapter0/dvr0 > bbc1.ts
> dvb-mplex -t MPEG2 -p 601 -q 600 -o bbc1.mpg -i TS_STREAM bbc1.ts
>
> will result in gibberish, infact dvb-mplex occasionally drops to the
> prompt with or sometimes without errors:
> A 10 second grab of video just now resulted in
>
>   Scanning audio stream for access units information
> Error in MPEG stream at offset (bits) 2232653: supposed marker bit not found.
>
> Another test just now resulted in:
>
>   Multiplexing file test.file.mpg
>     video PTS (3497.00ms) underflow at pack 1051 by 25.94ms
>     video PTS (3577.00ms) underflow at pack 1078 by 28.50ms
>     video PTS (3617.00ms) underflow at pack 1085 by 9.91ms
>     video PTS (3697.00ms) underflow at pack 1121 by 40.00ms
>     video PTS (3737.00ms) underflow at pack 1128 by 21.41ms
>     video PTS (6017.00ms) underflow at pack 1881 by 44.16ms
>     video PTS (6057.00ms) underflow at pack 1895 by 46.98ms
>     video PTS (7057.00ms) underflow at pack 2237 by 105.08ms
>     video PTS (7097.00ms) underflow at pack 2244 by 86.49ms
>     video PTS (7057.00ms) underflow at pack 2263 by 184.59ms
>     video PTS (7097.00ms) underflow at pack 2271 by 169.06ms
>     video PTS (7977.00ms) underflow at pack 2505 by 4.65ms
>     video PTS (8097.00ms) underflow at pack 2546 by 10.03ms
>     video PTS (8137.00ms) underflow at pack 2558 by 6.73ms
>     video PTS (8097.00ms) underflow at pack 2578 by 107.89ms
>     video PTS (8137.00ms) underflow at pack 2587 by 95.42ms
>     video PTS (9897.00ms) underflow at pack 3135 by 11.26ms
>     video PTS (9977.00ms) underflow at pack 3172 by 44.41ms
>     video PTS (10017.00ms) underflow at pack 3185 by 44.16ms
>     video PTS (9977.00ms) underflow at pack 3207 by 151.44ms
>     video PTS (10017.00ms) underflow at pack 3213 by 129.79ms
>     video PTS (13137.00ms) underflow at pack 4186 by 12.85ms
>     video PTS (13177.00ms) underflow at pack 4197 by 6.49ms
>     video PTS (13137.00ms) underflow at pack 4216 by 104.59ms
>     video PTS (13177.00ms) underflow at pack 4223 by 86.00ms
>     25 video underflows (SCR >= PTS or DTS)
>
> ts2ps | mplayer produces 100% bad result..
>
> I know BBC1 is a QAM16 channel.. whereas Chan4 isn't.. Ive tried dvbtune's
> scan_uk-t.sh script and it fails to see anything on the qam16
> multiplexes..
>
> dvbtune has not yet reported block errors, I've even reduced the delay
> between samples to see if I can spot an error, but no..
>
> Also dvbstream really does not seem to work, even on channel 4. It
> produces equally bad streams for any of the channels.. The problem is, I
> have a simple set of shell scripts I have used since about october last
> year and they have not changed.. they did work.. but now produce these
> corrupted results.. I previously did nothing more than call dvbstream -o
> -f<freq> <pid> <pid> with the -qam 16 -cr 3_4 for the qam16 mplexes..
>
> This should be the most basic way to view the video..
>
> Has work stopped on dvbstream and modifications to the driver now made it
> incompatible?
>
> Also, should I try running 2.5? On the ftp site it mentions that the
> saa7146 code is being rewritten for 2.5 then being back ported to 2.4 when
> proven stable. Is this now old news and the new re-written version been
> merged in?
>
> Does anyone know of any other things that might need adjusting in a system
> to get the card to work? such as IO-Apic which is active on this machine
> (its a single cpu p4)? Ive tried moving the dvb-t card between slots
> (there are only three in the system, the graphics card is on board (and
> not used)
>
> Ive also tried piping the data across the network in a tcp stream incase
> the disk io was causing the problem but the results were the same.
>
> Does anyone know of any reason why the QAM16 channels would be so bad in
> comparison to the regular multiplex which gets progressively worse the
> longer the capture/playback?
>
> Its all a bit confusing, especially since it worked almost perfectly at my
> last address (but admittedly in a different computer, with an ancient OS
> install of slackware 8.0)
>
> Cheers
>
> cp
>
> On 19 Jun 2003, Paul Andreassen wrote:
>
> > Hi, I'm a newbie too, so don't complain if I'm completely of track.
> >
> > >>From the dvdtune and tzap output it looks like your card is working
> > fine.  My guess is mplayer is broken.  Try xine (or sinek) instead.  And
> > also try saving a stream to your hard drive, stopping the DVB drivers
> > and playing it back.  This should tell you if its the drivers or not.
> >
> > Paul
> >
> > On Thu, 2003-06-19 at 11:39, Chris Pitchford wrote:
> > > Hi all,
> > >
> > > I was just wondering how things were progressing on this problem..
> > >
> > > Ive just reinstalled my machine after moving house and with the latest cvs
> > > snapshots of the linux-tv driver, dvbtune, dvbstream and libdvb I cannot
> > > get dvbstream to work using my old script. From the first frame rendered
> > > by mplayer (which has not been upgraded, it runs on a laptop) the image is
> > > corrupt with squeeking audio. Very different to my last experience at my
> > > old address about 3 months ago.
> > >
> > > Anyway, I have tried using tzap to tune and cat dvr0 to get the ts stream
> > > out and it does indeed work much better.. however, and this has been the
> > > problem more or less from day one when I get my Nova-t last year, the
> > > longer I leave the card running the greater the number of errors that will
> > > occur until (after about 5 minutes) mplayer will die
> > >
> > > Running dvbtune -m occasionally shows blockerrors of +1 for the first line
> > > when starting, but other than that its constant at zero..:
> > >
> > > Signal=11051, Verror=491, SNR=53199dB, BlockErrors=0, (S|L|C|V|SY|)
> > > Signal=11051, Verror=494, SNR=53713dB, BlockErrors=0, (S|L|C|V|SY|)
> > >
> > > As I copied those lines, mplayer was flickering and "squeeking" quite
> > > impressively! Ive seen errors caused in the stream when BlockErrors is not
> > > zero, but now its constantly zero yet these errors become more and more
> > > frequant as the minutes pass..
> > >
> > > I seem to be in the same boat and was wondering.. ah mplayer just died..
> > >
> > > @@@ libmpeg2 returned from sig11... (bad file?) @@@
> > > A:18448.2 V:18448.2 A-V:  0.051 ct: -0.023  4127/4127  13% 15%  6.4% 0 0 0%
> > > Broken frame at 0x3CCF30
> > > A:18448.5 V:18449.1 A-V: -0.596 ct: -0.052  4151/4151  13% 15%  6.4% 0 0 0%
> > > Successfully enabled DPMS
> > >
> > > .. was wondering if anyone had any idea why the card seems to gain
> > > errors.. If it was a signal strenth problem surely it would be from the
> > > moment mplayer started.. not good for 3 or 4 minutes, bad for another 2
> > > then fatal 2 or 3 after that?  Is this something to do with the tuner?
> > > possibly wondering off "lock"?
> > >
> > > Here's the first few lines from when tzap is started
> > > # ./tzap -r CHANNEL4
> > > using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
> > > tuning to 481833333 Hz
> > > status 0d | signal 2b2b | snr d2d2 | ber 0000ffff | unc 0000000b |
> > > status 1f | signal 2b2b | snr d0d0 | ber 000001f7 | unc 00000000 | FE_HAS_LOCK
> > > status 1f | signal 2b2b | snr cece | ber 000001f4 | unc 00000000 | FE_HAS_LOCK
> > > status 1f | signal 2b2b | snr d1d1 | ber 000001f1 | unc 00000000 | FE_HAS_LOCK
> > >
> > >
> > > I was wondering if there was something I could tweak or look at. Could it
> > > be faulty hardware? i'm using a standard Nova-t and really haven't had
> > > sustaineed luck with it. It works for periods then these errors creep in..
> > >
> > > Any help would be greatly appreciated
> > >
> > > Cheers
> > >
> > > cp
> > >
> > > On 8 Jun 2003, --[ UxBoD ]-- wrote:
> > >
> > > > > Okay getting a little better now - but I have noticed that when mplayer bails on me
> > > > > this is what is showing :
> > > > >
> > > > > @@@ libmpeg2 returned from sig11... (bad file?) @@@40  10%  5%  0.8% 0 0 9%%
> > > > >
> > > > > Any idea what causes this? would a dedicated MPEG card help this?
> > > >
> > > > > --
> > > > >
> > > > > // --[ UxBoD ]-- // 2.4.20-gentoo-r5 // Pentium(R) 4 CPU 2.53GHz //
> > > > > // gpg --keyserver wwwkeys.pgp.net --recv-keys 56ED1CB5 //
> > > > >
> > > >
> > >
> > --
> >
> >
>
>



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