[Mp4-tech] [H.264] IPCM

[Dzung Hoang]

Here are the steps to create a test image that forces IPCM.
1) Input a block of high-valued coefficients into the inverse 4x4 integer
transform. Clip the output block to the range [0,255].
2) Create an image that replicates the block computed in step 1.
3) Encode the image.
The above recipe creates an input pattern that would require many bits to
compress using the integer transform. The JM encoder would then be forced to
use IPCM.
Regards,
- Dzung Hoang
-----Original Message-----
From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Sebastián López
Suárez
Sent: Monday, January 15, 2024 7:02 AM
To: mp4-tech lists.mpegif.org
Subject: [Mp4-tech] [H.264] IPCM 
Dear experts,
I am testing a propietary decoder and, within this process, I would like
to verify if the decoder supports properly the decoding of IPCM. For that
purpose I have generated several bitstreams with differents sequences and
coding conditions, enabling for all the cases the use of IPCM mode
(EnableIPCM = 1 at encoder.cfg). However, as the IPCM is an extremely
unusual mode, in all the sequences the number of IPCM MBs was equal to
zero.
Does anyone knows how to force the reference encoder to produce some
IPCM macroblocks in a coded sequence? It can be made by simply modifying
the configuration file? If not, which C files should be modified?
Thank in advance.
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