[mythtv] pcHDTV oddity
jcw at wilsonet.com
Tue Sep 14 13:45:25 EDT 2004
Doug Larrick wrote:
> Jarod Wilson wrote:
>> Hey all,
>> 1) CBS in my area has one of the strongest signals, and only one
>> sub-channel. If I tune to it in live TV, 9 times out of 10, its
>> perfect. The other time, the picture is fine, but the audio sounds
>> like its muted and underwater. I can live with that, but *every*
>> recording (out of like 7 so far) done on that channel has the
>> underwater audio problem.
> Could it be that CBS is sending two audio programs, and one of them is
Doesn't look like they're sending two audio programs, but you'd know how
to interpret this better than I. (see below)
> Do you have access to another HDTV tuner that can switch
> between audio tracks?
> You could run my 'testinfo' stream-info program
> (<http://jekyl.no-ip.org/doug/testinfo.C>; 'testinfo /dev/dtv | more'
> after doing dtvsignal to change channels). Look for the TVCT
> (Terrestrial Virtual Channel Table) and see if it has multiple audio
> streams listed.
Okay, here's the TVCT stuff from testinfo:
************PSIP table type TVCT (Terrestrial Virtual Channel Table) size 62
Program #1: KIRO-DT, channel 7-1, source_id 1 **
Base PID 0011:
PID 0011, type video, language:
PID 0014, type AC3 audio, language: eng
Unsupported proto version 255
And for good measure, here's the output from dtvstream:
$ ./dtvstream -c 39 -q -v
Tuned "/dev/dtv" to channel 39.
Lost sync at input offset 0
Achieved sync after 79 bytes.
Summary after scanning first 20000 packets:
3 MBytes processed @ 15 Mb/s
54 pes_pkts processed
60 atsc_pkts, w/ distribution:
sst=2/2, mgt=52/1, vct=6/1, rrt=0/0,dcct=0/0, dccsct=0/0
Dropped pkts (Continuity Counter Errors) = 0
Active PIDs in this stream
PID=0x0, ctrl_type=PAT, pkt_cnt=15
PID=0x10, ctrl_type=PMT, pkt_cnt=16
PID=0x11, ctrl_type=VIDEO, pkt_cnt=15074
PID=0x14, ctrl_type=AUDIO_AC3, pkt_cnt=437
PID=0x1d00, ctrl_type=EIT, pkt_cnt=3
PID=0x1e01, ctrl_type=ETT, pkt_cnt=1
PID=0x1ffb, ctrl_type=ATSC, pkt_cnt=60
PID=0x1fff, ctrl_type=NULL, pkt_cnt=4394
Stream contains 2 total program(s).
Stream contains 1 valid program(s).
Using program 1: 7-1 KIRO-DT:
Audio (Dolby AC-3), language = eng
Maybe something to do with the 2 total programs, but only 1 valid? I
haven't a clue what the "Unsupported proto version 255" message from
testinfo means either. Slightly wonky audio stream perhaps? Odd that it
works 9/10 times in live TV but always fails on recordings though...
> There was some work done recently to allow Myth's libavcodec to deal
> with MPEG streams containing multiple audio programs, and switch among
> them. It might be worthwhile to pass (record) *all* the audio streams
> for a program in hdtvrecorder and see how well this works.
I'm assuming from the above output I'm only getting one audio program.
>> 2) ABC also has a very strong signal, and worked great several months
>> back when I last had my card working. I'm not sure if its related, but
>> this is my only 720p station... It always plays back like its in slow
>> motion, with stuttering video and audio, both in live TV and
>> recordings. If I pause the video, then unpause, it seems to play fine
>> for a sec, then starts crapping out again.
> What is your output device?
GeForce FX 5200 VGA output to Audio Authority 9A60 transcoder, custom
mode inside 540p timings fed to a high-def TV via component video. I
still need to get around to creating a viable 1080i mode...
HTimings 880 944 1048 1104
VTimings 480 506 520 563
Flags "+HSync" "+VSync"
> What refresh rate?
VertRefresh locked on 60.0 (hm, haven't tried 59.94...), HorizSync at 33.75.
> Can you post output of
> 'mythfrontend --verbose playback'?
Not at the moment, but I certainly will once I have an opportunity
(probably end-of-day). Thanks Doug!
Jarod C. Wilson, RHCE
jcw at wilsonet.com
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