Re: MPEG encoder API notes (Re: ANNOUNCE: ivtv alpha release)

[Gert Vervoort]

PlasmaJohn wrote:

I'm not real familiar with the MPEG specs either, but most of what you
enumerated here (and your next message) looks supportable by the iTVC15. I
don't remember any settings for the quantizer, but that may be a
register/mmio level operation which I don't have docs for.

The qmin/qmax settings I mention are specific for the VBR bitrate control of the SAA6752. Also the adaptive quantisation is specific for this IC. Other encoder might or might not use these kinds parameters, but I'm sure they have a slightly different meaning then.

The inter/intra quantiser matrices I mentioned are part of the MPEG video standard. The standard describes default matrices, but also custom matrices might be used. An encoder could implement fixed (default or custom) Q matrices or give make it programmable.

Perhaps we use this as the baseline, and the driver can reply with an
UNSUPPORTED message to any that it doesn't handle. For the properties that
tend to be card specific (noise reduction), those can be handled by userspace
tweak utilites.

Proberbly a custom ioctl could be used.

audio:

- type: MPEG, AC-3, LPCM

Layer I,II,III (iTVC15 does 1 & 2 but not 3)

For SAA6752 the MPEG audio is fixed to  MPEG1 layer 2.

Our chip can support AC3, but the card hardware isn't wired to support it as
far as I can tell.

- bitrate
- sampling frequency (DVD: 48 Khz, VCD: 44.1 KHz)

32KHz

This also a valid value. (althoug not support by SAA6752, which is fixed to 48kHz).

Trick Modes? (ff, rew)

Trick modes are a decoder issue. Does iTVC15 also have a MPEG decoder?

This raises a different topic, as my list was encoding specific.
MPEG encoding and decoding are very different issues, so a MPEG decoder will probarbly using a completely different API from an MPEG encoder.

There is a MPEG decoder API for the Stradis MPEG decoder card in V4L (ioctl: VIDIOCSWRITEMODE, VIDIOCSPLAYMODE), might be a starting point for a MPEG decoder API.

Copyright

This could also be set, I saw that SAA6752 has also a field "original".

Inverse Telecine

As far as I know not supported by SAA6752, but this is very usefull setting for 60 Hz contries.


Gert



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