我需要检测 RTP 数据包中的 VP8 关键帧。我知道如何删除 RTP 标头并获取有效负载。
它有特定的签名/标题吗?
VP8有一个RFC,它解释了如何检测帧是否是关键帧。请参见第 19.1 节。
| Frame Tag | Type |
| ------------------------------------------------- | ----- |
| frame_tag | f(24) |
| if (key_frame) { | |
| start_code | f(24) |
| horizontal_size_code | f(16) |
| vertical_size_code | f(16) |
| } | |
The 3-byte frame tag can be parsed as follows:
---- Begin code block --------------------------------------
unsigned char *c = pbi->source;
unsigned int tmp;
tmp = (c[2] << 16) | (c[1] << 8) | c[0];
key_frame = tmp & 0x1;
version = (tmp >> 1) & 0x7;
show_frame = (tmp >> 4) & 0x1;
first_part_size = (tmp >> 5) & 0x7FFFF;
---- End code block ----------------------------------------