字节流到NAL单位—视频解码

Question

I am working on direct show filter of H.265 decoder. I am using lide265 for this purpose.

The encoder returns byte stream. I need to convert it into NAL unit as per decoder requirement. How can I do that.

Because simple byte stream is not decoded.

Answer 1

Seems that H.265 byte stream syntax is very similar to H.264. If you take a look a the specification here :

byte stream NAL unit syntax!

leading_zero_8bits is a byte equal to 0x00.

NOTE – The leading_zero_8bits syntax element can only be present in the first byte stream NAL unit of the bitstream, because (as shown in the syntax diagram of clause B.2.1) any bytes equal to 0x00 that follow a NAL unit syntax structure and precede the four-byte sequence 0x00000001 (which is to be interpreted as a zero_byte followed by a start_code_prefix_one_3bytes) will be considered to be trailing_zero_8bits syntax elements that are part of the preceding byte stream NAL unit.

zero_byte is a single byte equal to 0x00.

When one or more of the following conditions are true, the zero_byte syntax element shall be present:

– The nal_unit_type within the nal_unit( ) syntax structure is equal to VPS_NUT, SPS_NUT or PPS_NUT.

– The byte stream NAL unit syntax structure contains the first NAL unit of an access unit in decoding order, as specified in clause 7.4.2.4.4.`

This should give you a notion when to expect 0x00000001 and when to expect 0x000001 and you should be able to parse the bitstream looking for the start codes and extracting the NAL units in between them.