[Live-devel] Found document about RTP payload format of ASF

[Derk-Jan Hartman]

On 3 jun 2009, at 17:17, Derk-Jan Hartman wrote:
> On 29 mei 2009, at 10:35, Ross Finlayson wrote:
>>> I know that live555 doesn't support X-ASF-PF format. And I 've  
>>> found a document (http://go.microsoft.com/fwlink/?LinkId=89814)  
>>> here (http://msdn.microsoft.com/en-us/library/cc245257(PROT. 
>>> 10).aspx). It mention about ASF file and also RTP payload format  
>>> of ASF. I think it will be useful for anyone want to write code to  
>>> handle this.
>>
>> Yes, if anyone were to implement this RTP payload format, I would  
>> likely add it to the released code.
>>>
>>> And one more thing, live555 doesn't support ASF, so why VLC player  
>>> use live555 library and it can play ASF ???
>>
>> Most likely because - in this case - VLC is downloading the file  
>> using HTTP, rather than RTSP.
>
> Much like MPEG-TS and MPEG-PS streams, ASF streams 'ASF files'. So  
> VLC opens a second demuxer for these streams, decodes the ASF  
> headers which are  in the Describe and feed them to this 2nd  
> demuxer, and then simply moves the ASF packets into the ASF demux.  
> It's not that hard to do, and you can easily get the required  
> information from the VLC source. We basically do the same with the  
> packets as we do with the packets we receive from MMS.
>
> Our implementation is not complete however, and it might be that we  
> are doing some things incorrectly. We basically just made a guess  
> about what would be in the packets we got from live555, based on our  
> knowledge about the MMS protocol. I'll open a bugticket in vlc with  
> this document so we can look at it more closely sometime.

I checked, and what VLC is doing is just skipping the first 4 bytes  
and praying it will work :D Which it surprisingly often actually does...
Must mean that the R, D and I bits are not that often set.

DJ