- Payload type 37 indicates the use of redundant encoding. The header
for every redundancy block is as shown below:
last (L): 1 bit set to 1 to indicate that this is not the final block.
payload type (PT): 7 bits.
block lenght (in bytes): 10 bits, not included this header.
- The last block contains the main data preceded by the following header:
- Payload type 38 indicates the use of high quality audio. The payload
type can be set either in the RTP header, in a redundancy block, or in
a last blcok. The high quality audio will be preceded by the following
header:
Earlier versions of Free Phone used the extension bit in RTP to indicate the use of redundant encoding in a packet. Starting with version 2.0b1, the extension bit is not used any more. Instead, special static payload types are used to encode redundant information and high quality audio. The decision to use static payload types was taken with our RAT colleagues at UCL while working together in the MERCI project .
last (L): 1 bit set to zero to indicate this is the final block.
payload type (PT): 7 bits.
