[Live-devel] StreamParser internal error (149999+ 4 >

[Jeff Shanab]

I thought the point of the NAL units was to manage size.
The key frame is the only worry and it gets broken into slices.
On one camera that has higer resolution I get a stream of nals like this

[7][8][5][5][5][1][1][1][1]....

Where the 7 and 8 are the sps and pps and are very small and the 5's represent slices of the large keyframe. (the ones are the much smaller difference frames)

From: live-devel-bounces at ns.live555.com [mailto:live-devel-bounces at ns.live555.com] On Behalf Of Ross Finlayson
Sent: Thursday, December 01, 2011 7:13 AM
To: LIVE555 Streaming Media - development & use
Subject: Re: [Live-devel] StreamParser internal error (149999+ 4 >

Surely the answer is to test the frame-size from the encoder before passing it into Live555

Unfortunately not, because we don't know the frame size in advance; we can figure it out only by parsing/copying the data, looking for the next 'start code'.  And it's this that's overflowing our stream parsing code.

On reflection, however, I think I can fix our H.264 parsing code to avoid this problem (the fix would be for H.264 parsing only).

However, you also should reconsider generating such huge NAL units.  The problem with NAL units this size is that if you stream them, then each such NAL unit will get fragmented over multiple RTP packets.  That's OK, but the loss of just one of these packets will cause the entire NAL unit to be undecodable by the receiver.  And the larger the NAL unit, the more likely that that will happen.

If you have control over your encoder, it would be far better to have it generate such large frames as multiple 'slices' - i.e., one NAL unit per slice, rather than as one NAL unit for the whole frame.

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

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