[mythtv-users] Audio squealing and hissing

[Christopher McCurdy]

On Saturday 17 March 2007 1:07:29 pm William Munson wrote:
> Christopher McCurdy wrote:
> > On Friday 16 March 2007 9:08:28 am William Munson wrote:
> >> Christopher McCurdy wrote:
> >>> My mythtv backend has a WinTV-Go for recording. Up until a month ago,
> >>> I was using RCA video output from my directv receiver plugged into the
> >>> composite input, and the RCA outputs from the satellite receiver
> >>> combined into a stereo plug and plugged into the line-in slot on the
> >>> card. Sound was fine, a little tinny, but it worked well enough. From
> >>> there, I daisy-chained the line-out of the WinTV card to the line-in
> >>> on my motherboard (snd_cmipci). Everything was good.
> >>>
> >>> But now I'm using the coax cable as the input. The sound works, but it
> >>> produces a horrible squeal louder than the program's audio, and
> >>> sometimes it just distorts things. I've heard some things come out
> >>> octaves lower than they should be, but sometimes there is just buzzing
> >>> and cracking... always louder than the program's audio.
> >>
> >> I am not an expert on this but from what I understand, If you use the
> >> coax input then you are using the audio decoder built into the capture
> >> card. This audio is generally carried over the pci bus. You also have a
> >> jumper between the WinTV and the sound card which duplicates the audio
> >> path and creates the echo. Try removing that cable, you may find it
> >> still works.
> >
> > I've tried to remove the cable patching line-out (WinTV) to line-in
> > (soundcard), but then I get no sound at all. I tried to change the audio
> > recording input to /dev/dsp1, since the snd_bt87x gets autoloaded, but
> > that also produces no sound. Logs show this whenever I try to use the
> > /dev/dsp1 input:
> >
> > NVR: Only read -1 bytes of 4096 bytes from '/dev/dsp1
> > read audio: Input/output error
> >
> > This is what my lspci says, though, so it seems I have audio capture.
> > Although should I open up my case and make sure I have the MSP34xx chip
> > on the board?
> >
> > 02:06.0 Multimedia video controller: Brooktree Corporation Bt878 Video
> > Capture (rev 11)
> >         Subsystem: Hauppauge computer works Inc. WinTV Series
> >         Flags: bus master, medium devsel, latency 32, IRQ 17
> >         Memory at df000000 (32-bit, prefetchable) [size=4K]
> >         Capabilities: [44] Vital Product Data
> >         Capabilities: [4c] Power Management version 2
> >
> > 02:06.1 Multimedia controller: Brooktree Corporation Bt878 Audio Capture
> > (rev 11)
> >         Subsystem: Hauppauge computer works Inc. WinTV Series
> >         Flags: bus master, medium devsel, latency 32, IRQ 17
> >         Memory at de800000 (32-bit, prefetchable) [size=4K]
> >         Capabilities: [44] Vital Product Data
> >         Capabilities: [4c] Power Management version 2
>
> Two things I can think of. First one, unless you have 2 capture cards
> your device should be /dev/dsp or /dev/adsp. The second thing I would
> try is to open whatever audio mixer program you use (alsamixer) and make
> sure that the appropriate audio input is not muted. After a reboot take
> a look at dmesg and see what devices your WinTV card attaches to and use
> them in the capture card setup in mythtv-setup.
>

I had assumed that since my sound card (CM8738) uses /dev/dsp, if I were to 
remove the patch cable, I should be recording audio directly from the TV 
card. Either way, I don't appear to have the MSP34xx chip that's needed for 
audio recording on the card.

bttv: driver version 0.9.16 loaded
bttv: using 8 buffers with 2080k (520 pages) each for capture
bttv: Bt8xx card found (0).
bttv0: Bt878 (rev 17) at 0000:02:06.0, irq: 17, latency: 32, mmio: 0xdf000000
bttv0: detected: Hauppauge WinTV [card=10], PCI subsystem ID is 0070:13eb
bttv0: using: Hauppauge (bt878) [card=10,autodetected]
bttv0: gpio: en=00000000, out=00000000 in=00ffffdb [init]
bttv0: Hauppauge/Voodoo msp34xx: reset line init [5]
bttv0: Hauppauge eeprom indicates model#44801
bttv0: using tuner=8
bttv0: i2c: checking for MSP34xx @ 0x80... not found
bttv0: i2c: checking for TDA9875 @ 0xb0... not found
bttv0: i2c: checking for TDA7432 @ 0x8a... not found
bttv0: i2c: checking for TDA9887 @ 0x86... not found
bttv0: registered device video0
bttv0: registered device vbi0
bttv0: PLL: 28636363 => 35468950 ..<5>sd 0:0:0:0: Attached scsi generic sg0 
type 0