On Mon, 9 Aug 2004 19:25:48 -0300 James Oakley <[EMAIL PROTECTED]> wrote:
> -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On August 9, 2004 09:45 am, Eric Jorgensen wrote: > > > > �I *do have an amp to receive AC3 streams, but i haven't yet > > > > tackled that. Currently my freevo system is a VIAC3, but so far i > > > > haven't found a way to get it to transmit anything but 48khz PCM. > > > > > > Put "-ac hwac3,mad, -srate 48000" in your MPLAYER_ARGS_DEF. > > > > It's the -srate argument i kinda have issues with. The specs from > > VIA > > for their chips imply that late enough versions (like mine) should not > > be restricted to 48khz. Support for this exists in late versions of the > > OSS driver, which, does not support digital out. > > IIRC, a DD amp will expect a 48kHz sample rate. Any other rate won't play > at the correct speed. Some hardware will resample the signal for you > automatically. My CMI8738 resamples *some* rates. Other hardware will > have drivers that perform the resampling. Some will happily pass the > wrong rate and it will sound odd. My brother's ALC650 passed 44.1kHz > audio without resampling which sounded slightly sped up. > > The -srate option in Mplayer will solve all of these problems. Well, you're wrong, in part. I'd been using -af resample, or something. I'm not sure, that box is offline right now. I'm not saying the quality was unacceptable. I'm saying i am intellectually and aesthetically irritated by the concept. I have a Sony receiver that actually tells me what the input it's receiving is - e.g. dolby 5.1, dts, etc - tells me a lot of things depending on what sort of audio is on a dvd in my dvd player. From mplayer, without resampling, the Sony says "PCM 48KHZ" and the playback sounds slightly tinny and slightly sped up. The IEC958 specification allows 32khz, 44.1khz, and 48khz. I imagine my receiver probably can handle any of these, but i don't have a way, offhand, to try. I have a limited number of devices with digital output, and i believe all my video devices do 48khz. It should certainly support 44.1khz, because this is the expected sample rate from a cd player. Computers on the other hand make things messier. The PC98 specification (from Microsoft) specified in no uncertain terms that audio hardware should do 48khz *only in order to be considered compliant. Microsoft frequently makes executive decisions based on the inability of their OS programmers to pull their heads out. They did away with ISA slots because their programmers never did figure out how to make ISA DMA access work properly without screwing the rest of your system. As a former OS/2 user and current Linux user, I know first hand that it CAN be done, but windows never did. Creative Labs cards, starting with the Live, and ending somewhere in the Audigy line, actually do this. The codec part on the board only receives 48khz, the DSP resamples everything to 48khz. The major difference between the Live and the Audigy was that they significantly improved their resampler code in the DSP. Other differences were just marketing fluff, or an outright lie. The Extigy, for example, is physically incapable of 24 bit audio *and 96khz sampling, directly contradicting the product specs. The "ac97" on-motherboard sound, until recently, nearly always followed this pattern. That's why you get bad audio on most of these under linux unless you resample. They didn't bother to implement resampling in hardware, or they do so poorly. VIA played along with this for quite some time, but recently stopped. If you have an 8233, 8233c, or 8235 (but not an 8233a), your on-motherboard sound controller supports multiple sample rates. Whether or not this is implemented on the board depends on (a) whether the ac97 codec part also supports it, (b) whether the manufacturer of the board implemented it correctly, and (c) whether the bios sets up the parts appropriately. This should be possible with alsa using dxs_support=1 or =4. I am under the impression that the Biostar board I'm using should have all the right parts(does have an 8235), but I'm not sure yet. I've been doing a lot of research recently, and like i said before, that box is offline right now. Then again, as long as it's gutted, i could figure out which ac97 chip is on the board and look up those specs. http://www.viaarena.com/?PageID=372 has some more information on this issue. ------------------------------------------------------- SF.Net email is sponsored by Shop4tech.com-Lowest price on Blank Media 100pk Sonic DVD-R 4x for only $29 -100pk Sonic DVD+R for only $33 Save 50% off Retail on Ink & Toner - Free Shipping and Free Gift. http://www.shop4tech.com/z/Inkjet_Cartridges/9_108_r285 _______________________________________________ Freevo-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/freevo-users
