Enhancements for ffmpeg 0.6.3 when dealing with live H264 stream

[ilevin]

Add abilities when writing to/reading from 3gp/mov format, and with no decoding/encoding (handling already encoding live stream from the net):

1. To store/retreive "btrt" bitrate box
2. Store/retreive "max NALU size" for H264 stream
3. Read "udta" box on a stream level

[Carl Eugen Hoyos]

Please provide samples for "btrt" and "udta" and please explain why "max NALU size" is needed.

[ilevin]

"max NALU size" was required in my project to be reported to the streamer, thus it will know whether transcoding is needed depending on remote end SDP negotiated abilities. For example, when streaming over network with MTU 1500, and negotiated mode 0 (disallowing fragmentation for H264 payload), transcoding is required if there is any NALU greater than 1468 in the stream. In my project, decision about switching transcoding on or off has to be taken upfront, thus knowing the maximum NALU size in all the packets in the stream is crucial.

"btrt" box serves similar purpose - we have restricted requirements on the high limits of the bit rate in the stream, and need to know maximum stream bit rate in a sliding window of a second upfront to decide whether trans-rating is required.
"udta" on a stream level may hold an SDP information in sub boxes, and we were required to utilize that info if it existed.

[Elon Musk]

Patches sent to tracker are ignored.

[Carl Eugen Hoyos]

Replying to richardpl:
I hope you'll find the ticket if such files ever appear...

[Mista_D]

​​http://www.mediafire.com/file/dwawitzp5xmc9vd/btrt.mp4

sample file with btrt atom