On 08/07/12 14:36, Markus wrote:
The minimum size of an RTP header is 12 byte. This means no CSRC
identifiers and no extension headers. Other than that, the rest is just
the payload. Depending on the actual payload size, this 12 byte overhead
can be significant to minimal. Therefore, it is necessary to find out
the packet size.
You can do this:
- a priori by estimating the packet size using the bitrate and frame
rate (example: 128kbit/s, 30 Hz -> 128000 / 8 / 30 ~ 534 byte for the
payload); this necessarily makes assumptions about the encoder, and you
have to add the RTP overhead yourself
- or a posteriori using buffer probes that you can hook up right at the
sink pad of the udpsink that is sending out the packets
I'd go the a posteriori way, since it makes no assumptions, and
implicitely adds the RTP overhead to the measurements. Gather
measurements over several seconds, and calculate the mean. It also makes
for pretty graphs over time :)
However, the a priori option can additionally be used to verify that
your bandwidth looks OK. (There are in fact statistical confidence
interval tests for this very purpose.)
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