Texas Instruments H.264 High Profile Encoder, Руководство пользователя

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B-1
Appendix B
Call Back function for NAL Units
Call back function provides compressed bit-streams to the application at NAL unit level. It is to
avoid point-to-point delay in the packed based transmission scenarios. H.264 allows dividing the
bit-stream of a frame in multiple NAL units (SPS, PPS, and slices). These NAL units can be
decoded independently. In situations where bit-stream of a frame is constituted of multiple NAL
units, it is ideal to transmit the first NAL unit while the encoder is encoding the second NAL unit.
This will help to reduce end-to-end delay compared to the case where the encoder is first encoding
all the NAL units and then transmitting them together.Call back function that consumes compressed
NAL units can be a simple copy function which reads from buffer (A) having compressed NAL unit
and writes to buffer (B) which constitutes the packet to be transmitted over network. The encoder
must be able to call it as and when it finishes producing one NAL unit. The usage of call back
function is captured in Figure 5-1and Figure 5-2.
Figure 5-1 Overview of callback function.