[FFmpeg-devel] [PATCH v4 2/4] libavformat/mxf: DNxUncompressed MXF related changes

[martin schitter]

On 10.09.24 15:14, Tomas Härdin wrote:
>> +++ b/libavformat/mxf.c

>> +    { { 0x06,0x0E,0x2B,0x34,0x04,0x01,0x01,0x01,0x0E,0x04,0x02,0x01,0x02,0x1E,0x01,0x00 }, 16,      AV_CODEC_ID_DNXUC }, /* DNxUncompressed/SMPTE RDD 50 */
> 
> Are really all 16 bytes significant?

I have to correct myself again:

This Entry in the "PictureEssenceCoding" list of 'mxf.c' should 
according to the specification look like:

+    { { 
0x06,0x0E,0x2B,0x34,0x04,0x01,0x01,0x0D,0x04,0x01,0x02,0x02,0x03,0x07,0x01,0x00 
}, 15,      AV_CODEC_ID_DNXUC }, /* DNxUncompressed/SMPTE RDD 50 */

The significant bit count is set to 15, because we do not support any of 
the extended fix point format variants.

But in practice I couldn't find such an entry in any of my test samples 
generated by DaVinci Resolve until now.


btw. there is an annoying flaw in the ffmpeg mxf parser:

The very common 'fill' boxes, which are used in DNxUncompressed files to 
align 'pack' boxes on 265 byte boundaries, are not recognized by ffmpegs 
mxf parser and generate lots of
"Dark key 06.0e.2b.34.01.01.01.02.03.01.02.10.01.00.00.00" warnings.


Martin