[Live-devel] Am I accidentally H.264 encoding twice???

[Ross Finlayson]

> WHAT?  Just a while ago I realized I'm passing H.264 encoded buffers to H264VideoStreamFramer, which is perhaps doubly encoding them to H.264 again.
> 
> Am I accidentally H.264 encoding twice?  Does the original ByteStreamFileSource fed to H264VideoStreamFramer feed raw buffers to H264VideoStreamFramer?

I think you're confused about what our software does.  *None* of our software does *any* encoding.  In particular, the "H264VideoStreamFramer" and "H264VideoStreamDiscreteFramer" classes each take - as input - already-encoded H.264 video data.   They don't do any 'encoding' (because the input data is already encoded.  All they do is parse the input H.264 video data, and output a sequence of H.264 'NAL units', with proper 'presentation time' and 'duration' values.

The difference between these two classes is that "H264VideoStreamFramer" takes - as input - H.264 video data that appears in a byte stream (e.g. a file or pipe).  "H264VideoStreamDiscreteFramer", on the other hand, takes as input discrete NAL units (i.e., one NAL unit at a time), *without* any preceding 'start code'.

So, the choice of which of these 'framer' classes to use depends on what kind of data comes out of your "MF_H264_DeviceSource" class.  If this class outputs an unstructured byte stream (that contains H.264 video data, with 'start codes' preceding each NAL units), then use a "H264VideoStreamFramer".  If, however, your "MF_H264_DeviceSource" class outputs a sequence of NAL units (one at a time, without a preceding 'start code'), then use a "H264VideoStreamDiscreteFramer" instead.

In either case, your 'framer' object should then be fed into a "H264VideoRTPSink" object, for streaming.

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/

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