[whatwg] Codecs for <audio> and <video>

[Maciej Stachowiak]

On Jun 30, 2009, at 1:59 AM, Silvia Pfeiffer wrote:

>
>>  - has off-the-shelf decoder hardware chips available
> "decoder hardware" for video means that there are software libraries
> available that use specific hardware in given chips to optimise
> decoding. It is not a matter of hardware vendors to invent new
> hardware to support Theora, but it is a matter of somebody
> implementing some code to take advantage of available hardware on
> specific platforms. This is already starting to happen, and will
> increasingly happen if Theora became the baseline codec.

I looked into this question with the help of some experts on video  
decoding and embedded hardware. H.264 decoders are available in the  
form of ASICs, and many high volume devices use ASICs rather than  
general-purpose programmable DSPs. In particular this is very common  
for mobile phones and similar devices - it's not common to use the  
baseband processor for video decoding, for instance, as is implied by  
some material I have seen on this topic, or to use other fully general  
DSPs.

Some H.264 ASICs are internally implemented as completely hardcoded  
logic. Others are implemented as a relatively general purpose DSP with  
a custom instruction set and microcode set by the manufacturer. Even  
these theoretically more general chips cannot be programmed by the  
device vendor, only the manufacturer of the chip itself. ASICs often  
have a significant cost and power consumption advantage compared to  
other solutions, at least in medium to high volume applications.

A Google search for "H.264 decoder ASIC" shows that these are  
available from many manufacturers: <http://www.google.com/search?q=H.264+ASIC 
 >.

As far as I know, there are currently no commercially available ASICs  
for Ogg Theora video decoding. (Searching Google for Theora ASIC finds  
some claims that technical aspects of the Theora codec would make it  
hard to implement in ASIC form and/or difficult to run on popular  
DSPs, but I do not have the technical expertise to evaluate the merit  
of these claims.)

Regards,
Maciej