Re: No audio in HW Compressed MPEG2 container on HVR-1300

[lawrence rust <lawrence@softsystem.co.uk>]

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@vger.kernel.org/msg21030.html

-- Lawrence Rust