Re: cmpci(4) and S/PDIF?
On Wed, Jun 15, 2011 at 05:24:20PM +0200, Christian Weisgerber wrote: Alexandre Ratchov: I would, but there shouldn't be anything required to make it work. The point of AC3/DTS pass-through mode is that it sends what looks like 16-bit stereo audio at the S/PDIF level. It's only the receiver that, on seeing a signature bit pattern, re-interprets the data and decodes it according to AC3 or DTS. So, I don't even understand how AC3 would work at all. I mean, a lot of programs (ie all using sio_onmove(3)) expect that one second of s16le at 48kHz be exactly 192000 bytes of data. If AC3 is used, that wouldn't be true anymore (AC3 is 320kbit/s iirc) and audio would be broken. Padding, of course. A video player like MPlayer will format the AC3 or DTS audio (both of which support numerous bit rates) in such a way that the result is a 192000 byte/s stream. The data on a DTS CD is already preformatted to 176400 byte/s and just needs to be passed through. I put the disk in, cdio cdplay, and the drive, cdio(1), and azalia(4) all think they are dealing with 44.1 kHz 16-bit stereo audio when in fact it is 6-channel DTS. As designed, S/PDIF only transmits 20(!)-bit stereo audio at various sample rates. However, ISO/IEC 61937 specifies how to carry various non-PCM audio formats over S/PDIF by formatting them like a 16-bit stereo stream. This is widely implemented for AC3 and DTS, rarely for MPEG audio. You're right. If data is properly padded, sndio can't make the difference between linear and compressed data (it counts bytes to extract the clock) And this can't be fixed without adding AC3 specific code. It is handled at the application level. Check out libmpcodecs/ad_hwac3.c in the MPlayer source. There is nothing OpenBSD-specific about this. It's the same for FreeBSD, Linux, and probably others. indeed no code is needed as long as padding is handled by apps. -- Alexandre
Re: cmpci(4) and S/PDIF?
On Fri, Jun 10, 2011 at 03:36:48PM +, Christian Weisgerber wrote: Jacob Meuser jake...@sdf.org wrote: Strangely, AC3/DTS pass-through does *not* work. there's this comment in cmpci.c: /* disable ac3 and 24 and 32 bit s/pdif modes */ and then the relevant register bits are cleared. feel free to play with making it work ;) I would, but there shouldn't be anything required to make it work. The point of AC3/DTS pass-through mode is that it sends what looks like 16-bit stereo audio at the S/PDIF level. It's only the receiver that, on seeing a signature bit pattern, re-interprets the data and decodes it according to AC3 or DTS. audio is not only about data transfers, it's also a clock source. AC3 data could be sent on the wire, but to make audio work at least the clock must be properly handled. So, I don't even understand how AC3 would work at all. I mean, a lot of programs (ie all using sio_onmove(3)) expect that one second of s16le at 48kHz be exactly 192000 bytes of data. If AC3 is used, that wouldn't be true anymore (AC3 is 320kbit/s iirc) and audio would be broken. And this can't be fixed without adding AC3 specific code. AFAICS, pass-through would be better outside the audio subsystem, after all AC3/DTS and friends is to transmit opaque data from one computer to another without processing it. While audio interfaces are to play and/or capture analog signals to process them. We don't use any AC3 mode for azalia(4) either and pass-through works there. I bet it only works in few special cases, probably because the clock is not involved -- Alexandre
Re: cmpci(4) and S/PDIF?
Alexandre Ratchov: I would, but there shouldn't be anything required to make it work. The point of AC3/DTS pass-through mode is that it sends what looks like 16-bit stereo audio at the S/PDIF level. It's only the receiver that, on seeing a signature bit pattern, re-interprets the data and decodes it according to AC3 or DTS. So, I don't even understand how AC3 would work at all. I mean, a lot of programs (ie all using sio_onmove(3)) expect that one second of s16le at 48kHz be exactly 192000 bytes of data. If AC3 is used, that wouldn't be true anymore (AC3 is 320kbit/s iirc) and audio would be broken. Padding, of course. A video player like MPlayer will format the AC3 or DTS audio (both of which support numerous bit rates) in such a way that the result is a 192000 byte/s stream. The data on a DTS CD is already preformatted to 176400 byte/s and just needs to be passed through. I put the disk in, cdio cdplay, and the drive, cdio(1), and azalia(4) all think they are dealing with 44.1 kHz 16-bit stereo audio when in fact it is 6-channel DTS. As designed, S/PDIF only transmits 20(!)-bit stereo audio at various sample rates. However, ISO/IEC 61937 specifies how to carry various non-PCM audio formats over S/PDIF by formatting them like a 16-bit stereo stream. This is widely implemented for AC3 and DTS, rarely for MPEG audio. And this can't be fixed without adding AC3 specific code. It is handled at the application level. Check out libmpcodecs/ad_hwac3.c in the MPlayer source. There is nothing OpenBSD-specific about this. It's the same for FreeBSD, Linux, and probably others. We don't use any AC3 mode for azalia(4) either and pass-through works there. I bet it only works in few special cases, probably because the clock is not involved And you will lose that bet. There is no theoretical reason why it shouldn't work, and in practice it does with everything I've thrown at it: * DVD audio tracks, AC3 (2.0, 4.1, 5.1; 192/224/384/448 kbit/s) and DTS (5.1; 768 and 1536 kbit/s) * DTS CD (44.1 kHz) * AC3 from digital television (2.0 and 5.1; 192/256/384/448 kbit/s) * DTS extracted from Blu-ray (at the maximum 1536 kbit/s) -- Christian naddy Weisgerber na...@mips.inka.de
Re: cmpci(4) and S/PDIF?
Jacob Meuser jake...@sdf.org wrote: Strangely, AC3/DTS pass-through does *not* work. there's this comment in cmpci.c: /* disable ac3 and 24 and 32 bit s/pdif modes */ and then the relevant register bits are cleared. feel free to play with making it work ;) I would, but there shouldn't be anything required to make it work. The point of AC3/DTS pass-through mode is that it sends what looks like 16-bit stereo audio at the S/PDIF level. It's only the receiver that, on seeing a signature bit pattern, re-interprets the data and decodes it according to AC3 or DTS. We don't use any AC3 mode for azalia(4) either and pass-through works there. The failure with cmpci(4) is quite mystifying. If you munge the bits of an AC3/DTS pass-through stream, for example by running it through aucat -v100, the signature will be destroyed and the receiver will simply treat the data as PCM audio. This doesn't happen here. My receiver seems to see a signature but never synchonize. -- Christian naddy Weisgerber na...@mips.inka.de
Re: cmpci(4) and S/PDIF?
Eventually I also picked up a Sweex SC015 card. (These are readily available in Europe at the time of writing.) cmpci0 at pci1 dev 2 function 0 C-Media Electronics CMI8738/C3DX Audio rev 0x10: ivec 0x7d5 audio1 at cmpci0 opl at cmpci0 not configured mpu at cmpci0 not configured Playing stereo audio at 44.1 and 48 kHz over S/PDIF works. The relevant mixer knob is this: playback.mode=dac [ dac spdif ] Set to spdif for S/PDIF output, dac (default) for analog output. This particular card also has a two-pin CD S/PDIF header. If you have an optical drive with a two-pin digital audio output, you can connect it to the card, and then enable a by-pass mode where audio from the drive is directly output to S/PDIF without the CPU having to read any data. The mixer controls involved are these: spdif.input=spdin1 [ spdin1 spdin2 spdout ] spdif.output=playback [ playback spdin ] Set spdif.input=spdin2 to select the CD input and spdif.output=spdin to direct it to the card's S/PDIF output. Strangely, AC3/DTS pass-through does *not* work. Neither for normal playback with MPlayer, nor for a DTS CD using the S/PDIF by-pass. My A/V receiver just remains silent or reports a decoding error. -- Christian naddy Weisgerber na...@mips.inka.de
Re: cmpci(4) and S/PDIF?
On Thu, Jun 09, 2011 at 05:01:39PM +, Christian Weisgerber wrote: Eventually I also picked up a Sweex SC015 card. (These are readily available in Europe at the time of writing.) cmpci0 at pci1 dev 2 function 0 C-Media Electronics CMI8738/C3DX Audio rev 0x10: ivec 0x7d5 audio1 at cmpci0 opl at cmpci0 not configured mpu at cmpci0 not configured Playing stereo audio at 44.1 and 48 kHz over S/PDIF works. The relevant mixer knob is this: playback.mode=dac [ dac spdif ] Set to spdif for S/PDIF output, dac (default) for analog output. This particular card also has a two-pin CD S/PDIF header. If you have an optical drive with a two-pin digital audio output, you can connect it to the card, and then enable a by-pass mode where audio from the drive is directly output to S/PDIF without the CPU having to read any data. The mixer controls involved are these: spdif.input=spdin1 [ spdin1 spdin2 spdout ] spdif.output=playback [ playback spdin ] Set spdif.input=spdin2 to select the CD input and spdif.output=spdin to direct it to the card's S/PDIF output. Strangely, AC3/DTS pass-through does *not* work. Neither for normal playback with MPlayer, nor for a DTS CD using the S/PDIF by-pass. My A/V receiver just remains silent or reports a decoding error. there's this comment in cmpci.c: /* disable ac3 and 24 and 32 bit s/pdif modes */ and then the relevant register bits are cleared. feel free to play with making it work ;) I imagine you'll need a mixer control to select ac3 mode. -- jake...@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org
Re: cmpci(4) and S/PDIF?
On Wed, May 04, 2011 at 05:35:07PM +, Christian Weisgerber wrote: Has anybody had success using the S/PDIF output of a cmpci(4) sound card? -- Christian naddy Weisgerber na...@mips.inka.de yes! my soundcard just arrived, which i bought for SPDIF playback with the C-Media chipset. sofar it works like a charm. here's how i got it working: aucat -r 44100 -b 8192 -l mixerctl -t playback.mode # this puts it in SPDIF playback mode dmesg specs: cmpci0 at pci3 dev 0 function 0 C-Media Electronics CMI8738/C3DX Audio rev 0x10: apic 2 int 20 model: Sweex SC015, 7.1 PCI Sound Card (http://www.sweex.com/SC015)
Re: cmpci(4) and S/PDIF?
On Wed, May 11, 2011 at 03:36:47PM +0200, David Steiner wrote: On Wed, May 04, 2011 at 05:35:07PM +, Christian Weisgerber wrote: Has anybody had success using the S/PDIF output of a cmpci(4) sound card? -- Christian naddy Weisgerber na...@mips.inka.de yes! my soundcard just arrived, which i bought for SPDIF playback with the C-Media chipset. sofar it works like a charm. here's how i got it working: aucat -r 44100 -b 8192 -l mixerctl -t playback.mode # this puts it in SPDIF playback mode dmesg specs: cmpci0 at pci3 dev 0 function 0 C-Media Electronics CMI8738/C3DX Audio rev 0x10: apic 2 int 20 model: Sweex SC015, 7.1 PCI Sound Card (http://www.sweex.com/SC015) if you do aucat -i /dev/zero, does the server crash after a certain amount of time? -- Alexandre
Re: cmpci(4) and S/PDIF?
On Wed, May 11, 2011 at 05:23:36PM +0200, Christian Weisgerber wrote:
In article 20110511133647.ga3...@mango.fritz.box you write:
Has anybody had success using the S/PDIF output of a cmpci(4) sound
card?
yes! my soundcard just arrived, which i bought for SPDIF playback with the
C-Media chipset. sofar it works like a charm. here's how i got it
working:
mixerctl -t playback.mode # this puts it in SPDIF playback mode
Can you send me the output of mixerctl -v please?
--
Christian naddy Weisgerber na...@mips.inka.de
$ mixerctl -v
inputs.dac=192,192 volume
inputs.dac.mute=off [ off on ]
inputs.fmsynth=192,192 volume
inputs.fmsynth.mute=off [ off on ]
inputs.cd=0,0 volume
inputs.cd.mute=on [ off on ]
inputs.line=0,0 volume
inputs.line.mute=on [ off on ]
inputs.aux=0,0 volume
inputs.aux.mute=on [ off on ]
inputs.mic=0 volume
inputs.mic.mute=on [ off on ]
inputs.mic.preamp=off [ off on ]
inputs.spkr=128 volume
record.source= { mic cd line aux wave fmsynth spdif }
record.mic=0 volume
playback.mode=spdif [ dac spdif ]
spdif.input=spdin1 [ spdin1 spdin2 spdout ]
spdif.input.phase=positive [ positive negative ]
spdif.output=playback [ playback spdin ]
spdif.output.playback=wave [ wave legacy ]
spdif.output.voltage=5V [ 5V 0.5V ]
spdif.monitor=spdout [ off spdin spdout ]
outputs.master=128,128 volume
outputs.rear=off [ off on ]
outputs.rear.individual=off [ off on ]
outputs.rear.reverse=off [ off on ]
outputs.surround=off [ off on ]
Re: cmpci(4) and S/PDIF?
David Steiner davidsteiner2...@gmail.com wrote: yes! my soundcard just arrived, which i bought for SPDIF playback with the C-Media chipset. sofar it works like a charm. here's how i got it working: aucat -r 44100 -b 8192 -l mixerctl -t playback.mode # this puts it in SPDIF playback mode dmesg specs: cmpci0 at pci3 dev 0 function 0 C-Media Electronics CMI8738/C3DX Audio rev 0x10: apic 2 int 20 model: Sweex SC015, 7.1 PCI Sound Card (http://www.sweex.com/SC015) Hmm. I have a similar card (it has only four analog jacks and an additional joystick port) with the very same chipset... cmpci0 at pci4 dev 6 function 0 C-Media Electronics CMI8738/C3DX Audio rev 0x10: apic 2 int 20 ... but I can't get it to output anything on the S/PDIF port. Mysterious. I'm beginning to wonder if the port on my card is simply shot. -- Christian naddy Weisgerber na...@mips.inka.de
cmpci(4) and S/PDIF?
Has anybody had success using the S/PDIF output of a cmpci(4) sound card? -- Christian naddy Weisgerber na...@mips.inka.de
