问题
I try to find any info about AAC HEv2 (PS) in an MPEG Transport Stream (TS) for HLS.
According to the HLS Authoring Specification for Apple Devices AAC HEv2 is a supported format. AAC HEv2 is part of MPEG-4, but I cannot understand how HEv2 could fit into a transport stream.
SBR (or HEv1) can be in TS by implicit signaling. In case of MP4 we have an audio specific config. But how can I multiplex AAC Parametric Stereo into the TS?
Is it available or not?
I cannot find any info from the Apple site and so on.
回答1:
There are two ways to put AAC into transport stream.
1. Using ADTS syntax (MPEG2-style).
In a such case PMT's stream_type should be specified as 0x0F (ISO/IEC 13818-7 Audio with ADTS transport syntax).
So, you are limited to using "old" (MPEG2) AAC versions only, without SBR and PS.
2. Using LATM+LOAS/AudioSyncStream syntax (MPEG4-style).
In a such case PMT's stream_type should be specified as 0x11 (ISO/IEC 14496-3 Audio with the LATM transport syntax).
And you can use all the force of "new" (MPEG4) AAC features, including SBR and PS.
Furthermore, DVB standard ETSI TS 101 154 demands: HEv1/HEv2 AAC shall be transmitted using LATM syntax.
来源：https://stackoverflow.com/questions/49006675/incorporate-hev2-aac-into-an-mpeg-ts-for-hls-content