Aw: Re: What is the alignment capability in video/x-h264

pfarmer flacone at
Mon Feb 24 00:55:21 PST 2014

Thanks again for your comments. 


My plan was to send different NALU types via a different transport channel with configurable Quality of Service. Such that non Video Coding Layer NALUs (e.g. SPS and PPS) can be send via a  more reliable channel. It appeared to me more straight forward to handle each NALU as they are produced and not placed in a container already. 

But indeed the overhead will be marginally and I will use the h264parse element functions which will give my transport payloader the NALUs seperated. 

On the receiver side I will place the h264parse element in fornt of the decoder (avdec_h264). 



Gesendet: Samstag, 22. Februar 2014 um 18:13 Uhr 
Von: "Tim Müller [via GStreamer-devel]" <ml-node+s966125n4665440h42 at> 
An: pfarmer <flacone at> 
Betreff: Re: What is the alignment capability in video/x-h264 

On Sat, 2014-02-22 at 04:47 -0800, pfarmer wrote: 

> > What's not "possible" exactly? 
> It is not possible to output NALU aligned buffers from the x264enc 
> element (as it wasn't in gstreamer0.10 either). 

Well, the output of x264enc is always also NALU aligned, since AU 
alignment is a subset of NALU alignment. Where does it make a difference 
for you? Is it just about the caps, or something else? The only 
difference I can think of is that if you could get the encoder to output 
a partial frame already you have marginally lower latency. Whether x264 
actually supports that, I don't know (but didn't check). Most encoders 


>  It is also not possible to give NALU aligned buffers to the 
> avdec_h264 element. 
> The reason is that I want to built my own packetizer for another 
> transport protocol. For this, it would be sufficient/easier to get the 
> NALUS directly. 

There was parsing done inside ffdec_h264, now parsing is done in 
h264parse. Why not just put an h264parse in front of avdec_h264? Is it 
about parsing overhead, or caps or.. ? 


Tim Müller, Centricular Ltd - 

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