Dear Wiki user, You have subscribed to a wiki page or wiki category on "Freevo Wiki" for change notification.
The following page has been changed by 219.93.2.16: http://freevo.sourceforge.net/cgi-bin/moin.cgi/FrequentlyAskedQuestions The comment on the change is: Updated info on dma audio capture for mencoder, saa7134 ------------------------------------------------------------------------------ @@ -282,7 +282,7 @@ The btaudio kernel module provides an alternate method of recording or playing sound from bt878 tv-tuner cards directly via the PCI bus, bypassing the sound card input -and potentially results in better A/V sync. +and potentially results in better A/V sync. This is termed 'DMA Audio'. For tv-tuner cards using other chipsets (e.g., Phillips SAA7134, Conextant cx88) there are equivalent capabilities available. @@ -337,7 +337,7 @@ btaudio: using card config "default" btaudio: registered device dsp1 [digital] }}} -For tvmixer you probbly do not need to use any options so simply: +For tvmixer (needed by btaudio only, not necessary for saa7134-based cards) you probably do not need to use any options so simply: {{{ # modprobe tvmixer }}} @@ -351,14 +351,25 @@ Ok, with any luck you now have these modules loaded. It is time to try them out. If you have a silly audio patch cable going from your tv card to your -sound card remove now because you won't be needing it! +sound card remove now because you won't be needing it! But first please read caveat below. -Not all programs are capable of capturing audio using btaudio. A few -requirements come to mind. You must be able to tell the program to capture +Not all programs are capable of capturing audio using DMA audio via the PCI bus. +Notably, most TV viewing programs (such as tvtime, mplayer, xawtv 3.x) are +not able to use the DMA audio input for live viewing. This situation may change in future +as DVB (digital video broadcast) capture cards become more common. + +The tvtime FAQ notes a workaround for live TV viewing without the audio patch cable. +See http://tvtime.sourceforge.net/help.html#noaudio + +Hence, DMA audio capture is currently limited to recording TV programs for later viewing. +A few requirements come to mind. You must be able to tell the program to capture at a sample rate equal to what btaudio is providing. The default for btaudio is a rate of 32000 Hz. Most programs will try to capture at a rate of 44100 Hz so if you can't tell them otherwise what you hear will sound like -Alvin and the Chipmunks :). Also you will need to specify which DSP resource +Alvin and the Chipmunks :). For saa7134-based TV-capture cards, the audio rate +must be set to 32000 Hz or you won't get any sound! + +Also you will need to specify which DSP resource to capture from, and sometimes which channel (line-in). For me the DSP for my digital btaudio device is /dev/dsp1 as shown in the above kernel messages. There are also some other problems that occur when it comes to programs using @@ -368,7 +379,7 @@ attempting to access a btaudio device. Some of the time this can be worked around by patching or editing the source code of the offending program. -Mplayer by default does not work with btaudio, that also includes mencoder. +Current versions of mencoder (1.0preX) has support for DMA audio. Another program that needs some help is mp1e. There is a quick patch that can be applied to mp1e and it can be found in Aubin's freevo WIP directory, 'freevo/WIP/Aubin/mp1e_btaudio.diff'. @@ -407,10 +418,12 @@ {{{ mencoder -tv on:driver=v4l:input=0:norm=NTSC:channel=2:chanlist=us-cable:\ width=320:height=240:outfmt=yv12:device=/dev/video0:adevice=/dev/dsp2:\ -audiorate=32000:buffersize=64 -ovc lavc -lavcopts vcodec=mpeg4:\ +audiorate=32000:buffersize=64:forceaudio:forcechan=1 -ovc lavc -lavcopts vcodec=mpeg4:\ vbitrate=1200:keyint=30 -oac mp3lame -lameopts br=128:cbr:mode=3 -ffourcc divx -o /mnt/video/06-08_07:30_-_Seinfeld.avi ,2 WNYFLP" key parameters: adevice=/dev/dsp2 - analog btaudio audiorate=32000 - proper sampling rate + forceaudio - needed for mencoder to force recording of audio + forcechan=1 - try 2 for stereo mode if your capture card supports it }}} ------------------------------------------------------- This SF.Net email is sponsored by: YOU BE THE JUDGE. Be one of 170 Project Admins to receive an Apple iPod Mini FREE for your judgement on who ports your project to Linux PPC the best. Sponsored by IBM. Deadline: Sept. 24. Go here: http://sf.net/ppc_contest.php _______________________________________________ Freevo-wikilog mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/freevo-wikilog
