VC1 bitstream format for Simple/Main profile

[adamm]

Hello,

Does anyone have experience with VC1 bitstreams for Simple/Main profiles? Annex L of SMPTE 421M specification is dedicated to Bitstream Metadata Serialization, but it seems like it's not applicable to Simple/Main profiles.

According to http://read.pudn.com/downloads50/doc/fileformat/172350/vc1%20encoding.pdf the structure of headers for Simple/Main profiles should look like this:

if( start_code == 0x0000010F ) //Sequence start code
{                
frame_width       16         uimsbf         
frame_height      16         uimsbf         
STRUCT_C()        32         bslbf                                     
start_code        32         0x0000010D         
}                                                                                                                                                                                                                                                                                                                                 
else if (start_code == 0x0000010D ) //Frame start code
{                
}

which is different than Annex L of SMPTE 421M specification. So, does anyone know what kind of headers should I add to VC1 frames in order for decoder to have all information necessary for the decoding process?

[Marsia Mariner]

.........

So, does anyone know what kind of headers should I add to VC1 frames in order for decoder to have all information necessary for the decoding process?

First of all: WHY would you want to do that

Because WMV9 was originally developed as a codec for PC playback, it had an inherent dependency on its file container (ASF, AVI) to carry sequence header and picture size metadata necessary to correctly decode the picture. When VC-1 standardization process began and Advanced Profile was being designed, one of the key goals of Advanced Profile was to make it container and transport independent so that it could exist as a standalone elementary stream. "WMV9 classic" became VC-1 Simple/Main and most of its features were just grandfathered in.

So VC-1 Advanced Profile is the only VC-1 profile that is self-contained - it carries sequence header and picture size metadata in the bitstream. This allows the creation of VC-1 elementary streams (.vc1).

The RCV format was created to provide a lightweight encapsulation method for VC-1 Simple and Main bitstreams. It's not a full file format - it's just a simple overhead that provides sequence header and picture size information for the bitstream. Annex J and L of the SMPTE VC-1 specification describe the bitstream syntax

{{ source: https://forum.doom9.org/showthread.php?p=1060034#post1060034 }}

I suppose it's not impossible to do what you intend to do, but... would it be worth the effort?
Even Microsoft themselves don't care about WMV3 and WVC1 anymore

P.S.: I think this thread should be moved to the Programming forum.

[adamm]

Thank you for answering.

WHY would you want to do that

I am learning about codecs, and I have decoder that supports simple/main profile bitstreams and want to test it.
So far I could only get some of the pictures from streams (probably I frames) using headers shown in the code I put in first post. It seams like decoder needs some more information, but I am not sure what.

The RCV format was created to provide a lightweight encapsulation method for VC-1 Simple and Main bitstreams.

I was not able to find the RCV format specification... Does anyone have more info about that format? I have tried with Annex L format, but with no luck.

[Marsia Mariner]

I was not able to find the RCV format specification... Does anyone have more info about that format? I have tried with Annex L format, but with no luck.

I think /hope this piece of code may help you:

https://codecs.multimedia.cx/?p=131