http-live-stream 协议ID3 tag和 timestamp

来源：互联网发布：网络营销策划书的结构编辑：程序博客网时间：2024/06/15 21:01

一般的HLS 码流没有ID3 tag，都是0x47 开头的标准TS流， Nuplayer 会检查标准TS流，如果不是TS 流，才会走到检查ID3 tag。

一般 TS码流的同步头有问题才会走到ID3 tag检查。

http live stream 协议中，定义了audio packet 必现带有ID3 tag，并且必现带有私有的“com.apple.streaming.transportStreamTimestamp”标识符，紧跟着真正的时间戳。

Nuplayer 中的PlaylistFetcher 中实现这块代码， ffmpeg 中的hls.c 也实现了同样的代码。

协议定义：https://tools.ietf.org/html/draft-pantos-http-live-streaming-23

3.4.  Packed Audio
   A Packed Audio Segment contains encoded audio samples and ID3 tags   that are simply packed together with minimal framing and no per-   sample timestamps.  Supported Packed Audio formats are AAC with ADTS   framing [ISO_13818_7]; MP3 [ISO_13818_3]; AC-3 [AC_3]; and Enhanced   AC-3 [AC_3].   A Packed Audio Segment has no Media Initialization Section.   Each Packed Audio Segment MUST signal the timestamp of its first   sample with an ID3 PRIV tag [ID3] at the beginning of the segment.   The ID3 PRIV owner identifier MUST be   "com.apple.streaming.transportStreamTimestamp".  The ID3 payload MUST   be a 33-bit MPEG-2 Program Elementary Stream timestamp expressed as a   big-endian eight-octet number, with the upper 31 bits set to zero.   Clients SHOULD NOT play Packed Audio Segments without this ID3 tag.

阅读全文

0 0