[libav-devel] [RFC] Cineform HD questions

Kostya Shishkov kostya.shishkov at gmail.com
Thu Dec 31 07:17:13 CET 2015


On Thu, Dec 31, 2015 at 04:13:50AM +0000, Kieran Kunhya wrote:
> 
> This patch is the first attempt at getting a working Cineform HD decoder into avcodec
> It supports YUV422P10 files which are the majority of files in the wild
> There are some files not supported such as those from film scanners and some older files which do something unusual with chroma and the transform.
> Also files which are cut awkwardly will infinite loop in the coefficient decoding because of a lack of escape symbol.

A simple condition for checking if you exceeded number of coefficients will be
added anyway (probably by you too).

> The big question is how to organise the coefficients - at the moment all the buffers are hardcoded.
> If anyone has any suggestions about the best way to do this, that would be appreciated.

1) find somebody who can convert transform into lifting scheme so you can do
it inplace (yes, very realistic)
2) have one temporary buffer for merging and store all bands in the same
plane:

   (coeffs)             (tmp)        (coeffs again)
LL0 | LH0 |  LH1       L0           band0   |  LH1
----+-----+            ---                  |
HL0 | HH0 |        =>  H0     =>            |
----+-----+------                   --------+------
   HL1    |  HH1                    HL1     |  HH1

So you'll have the same stride for input high and low coeffs too.

    Captain Obvious' sidekick signing out.


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