Differences between avc1 and h264 during h264/AVC Video decoding

Differences between avc1 and h264

Http://blog.csdn.net/qiuchangyong/article/details/6660253

H.264 video types

The following media subtypes are defined for H.264 video.
Subtype fourcc description
Mediasubtype_avc1 'avc1 'H.264 bitstream without start codes.
Mediasubtype_h264 'h264' H. 264 bitstream with start codes.
Mediasubtype_h264 'h264' equivalent to mediasubtype_h264, with a different fourcc.
Mediasubtype_x264 'x264' equivalent to mediasubtype_h264, with a different fourcc.
Mediasubtype_x264 'x264' equivalent to mediasubtype_h264, with a different fourcc.

 

The main difference between these media types is the presence of startcodes in the bitstream. If the subtype is mediasubtype_avc1, thebitstream does not contain start codes.

 

 

Differences between avc1 and h264 during h264/AVC Video decoding

Http://blog.csdn.net/ameyume/article/details/7542979

Fourcc: avc1 Description: H.264 bitstream without start codes.
Fourcc: h264 Description: H.264 bitstream with start codes.

H.264 bitstream with start Codes

H. 264 bitstreams that are transmitted over the air, or contained in MPEG-2 program or transport streams, or recorded on HD-DVD, are formatted as described in Annex B of ITU-T rec. h.264. According to this specification, the bitstream consists of a sequence of network protocol action layer units (nalus), each of which is prefixed with a start code equal to 0x000001 or 0x00000001.
H.264 video with a starting code is generally used for wireless transmission, wired broadcast, or HD-DVD. The start code of these data streams is 0x000001 or 0x00000001.


H.264 bitstream without start Codes

The MP4 container format stores H. 264 data without start codes. instead, each NALU is prefixed by a length field, which gives the length of the NALU in bytes. the size of the length field can vary, but is typically 1, 2, or 4 bytes.
This section roughly means that H.264 videos without a starting code are mainly stored in MP4 files. Its data streams start with 1, 2, or 4 bytes to indicate the length of data.

In the original article, "NALU" is simply the most basic unit in H.264 format and a data packet.

 

Differences between avc1 and h264 during h264/AVC Video decoding