[FFmpeg-devel] GSoC VQA v3 : some more help needed

The Deep Explorer thedeepexplorer
Sat Apr 4 23:02:36 CEST 2009

Hi all,
    I need some help in understanding how each frame is decoded in
 VQA v3. Please let me know how to proceed on the following :

1) VPTR Decoding

Steps :

Read 1 short int ( 2 bytes)

Read bits 15,14,13 and based on the command do actions.

The document says e.g. :

     a) 000 - Skip Count blocks. Count is (Val & 0x1fff).

        What is the Count blocks ?
        What is this Val and where am I supposed to get it from ?

     b) 001 - Write block number (Val & 0xff) Count times.
              Count is (((Val/256) & 0x1f)+1)*2. Note that this can
              only index the first 256 blocks.

              What is the block number ?

<<Every row of blocks is processed individually of others.
When you encounter the end of a row, proceed to the next row
(blocks are processed left to right, top to down).
Repeat this process until all blocks in the frame are covered and
that's it!>>

So is this the layout mechanism for v3 ? How are Count, Block, and Val
are related.

There are two for loops, first one for the  y axis and the second one for
the x axis for the v1 and v2. so in case3 will the decoding of vptr will take
place ? Read the three bits and then do the actions as specified ?

2) For VPRZ, first decode it with format80 and then follow the vptR thing
   so the VPRZ is dependent on the VPTR :)

I will wait for the replies :)


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