On Mon, 2010-08-02 at 14:15 +1200, Shane Harrison wrote: > Hi There, > > I am having a problem with getting an audio stream present in the > MPEG2 stream from an HVR-1300 card. [snip] > Problem > ~~~~~~ > The delivered MPEG-2 stream generally has no audio component. Mplayer > reports "no audio found". > > The same problem exists for both TV input and composite input. By > repeatedly switching between the TV input and the Composite input we > can eventually get an audio component in the MPEG-2 stream. > Thereafter we always get the audio component until a power off and > restart. Simply rebooting (no power off) seems to still leave things > in a state where the audio component is in the MPEG-2 stream. > > There is a second problem, the audio stream always contains white > noise (I assume TV tuner noise - we don't have it tuned nor an aerial > attached) mixed with the signal applied to the analog in ports. > > Analysis > ~~~~~~ > The most likely scenario is that the hardware is not being initialised > correctly most of the time, once it is initialised correctly then it > works thereafter. Unfortunately it is difficult to determine the > actual audio path being used. Clearly the audio comes into the WM8775 > (DAC) via a bus switch that switches between the composite/audio on > the back panel and the white header. It then enters the CX2388x via > the I2S input pins. We initially assumed that the audio was then > routed through to the CX23416 (MPEG Encoder) via the I2S output pins > of the CX2388x, but we have begun to doubt this assumption since the > CX2388x is set in normal mode by the drivers and the captured audio > doesn't reflect the bit patterns we see on the I2S Data Out line using > an oscilloscope. That is, when we apply *no* signal to the analog > input, the I2S Dout line is "quiet" yet we hear white noise. > > Questions > ~~~~~~~~ > 1) Anyone have any similar experiences? This sounds very much like the problems that I had with my Nova-S-plus card while developing a patch to capture line-in audio with composite video. Looking at the docs for the wm8775 it appeared that it wasn't being correctly initialised. I also found need to change the cx88 code to mute/un-mute audio in. Maybe you should try applying this patch, I posted it to this group on Saturday - see. http://www.mail-archive.com/linux-media@xxxxxxxxxxxxxxx/msg21030.html -- Lawrence Rust -- 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
