Em Mon, 16 Jun 2014 15:04:44 -0400 Devin Heitmueller <dheitmueller@xxxxxxxxxxxxxx> escreveu: > >> The official TV playback application, found on the CD with drivers, > >> captures samples from the card into its buffer, and plays from the other > >> end of the buffer concurrently. If there are, on average for a few > >> seconds, too few samples in the buffer, it means that they are consumed > >> faster than they arrive, and so the SAA chip is told to produce them a > >> bit faster. If they accumulate too much, the SAA chip is told to produce > >> them slower. That's it. > > > > Ok. Well, xc5000 (with does the audio sampling) doesn't have it, AFAIKT. > > > >> > > >> > The xc5000 tuner used on this TV device doesn't provide any mechanism > >> > to control audio PLL. It just sends the audio samples to au0828 via a > >> > I2S bus. All the audio control is done by the USB bridge at au0828, > >> > and that is pretty much limited. The only control that au0828 accepts > >> > is the control of the URB buffers (e. g., number of URB packets and > >> > URB size). > > It's probably worth noting that Mauro's explanation here is incorrect > - the xc5000 does *not* put out I2S. It outputs an SIF which is fed > to the au8522. The au8522 has the audio decoder, and it's responsible > for putting out I2S to the au0828. > > Hence the xc5000's PLL would have no role here. > Ah, OK. I didn't notice that hvr950q was using SIF. In this case, then maybe au8522 may have some PLL fine tune register to adjust the sampling rate. > In fact, you should see the exact same behavior on the A/V input, > since the au8522 is responsible for the I2S clock which drives the > cs5503 (the 5503 is in slave mode). I suspect that the best is to use a resampling code to avoid the frequency drift clock issue, as it is generic enough to cover both cases, and won't require hardware-assisted support. Yet, as I posted on my previous email, this is not yet the kind of bug that we're facing right now. If I'm doing the calculus correct, a -10Hz difference at a 48 kHz sampling rate would take ~150 seconds to cause an underrun (a 16 ms period_bytes lost). Regards, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
