updating definition of sample (#76)

* Update apv_isobmff.md

adding the length field for au for the format of sample.

Signed-off-by: Youngkwon Lim <yklwhite@gmail.com>

* added cross reference

Signed-off-by: kp5.choi@samsung.com <kp5.choi@samsung.com>

* fixed typo and removed useless whitespace

Signed-off-by: kp5.choi@samsung.com <kp5.choi@samsung.com>

---------

Signed-off-by: Youngkwon Lim <yklwhite@gmail.com>
Signed-off-by: kp5.choi@samsung.com <kp5.choi@samsung.com>
Signed-off-by: Computational Photography and Cinematography <125966497+cpncf@users.noreply.github.com>
Co-authored-by: kp5.choi@samsung.com <kp5.choi@samsung.com>
Co-authored-by: Computational Photography and Cinematography <125966497+cpncf@users.noreply.github.com>

Author: 3 people

readme/apv_isobmff.md

@@ -63,7 +63,7 @@ aligned(8) class APVDecoderConfigurationBox extends FullBox('apvC',version=0, fl
 }
 ~~~~
 
-## APV Decoder Configuration Record {#APVDecoderConfigurationRecord}		
+## APV Decoder Configuration Record {#APVDecoderConfigurationRecord}
 
 The APVDecoderConfigurationRecord contains the information for initial configuration of a decoder which consumes the samples references the sample entry type of apv1. The information in this record is extracted from frame_header() of the bitstream stored in the track containing this record.
 
@@ -159,20 +159,7 @@ the full_range_flag field in the frame header of the frames whose value of the p
 ## APV Sample Description
 
 ###	Format of sample
-When APV coded bitstream is encapsulated in a track with APVSampleEntry, each sample shall contain a size of access unit and an access unit of APV coded data.
-
-~~~~
-aligned(8) class APVSample{
-    unsigned int(32) au_length;
-    bit(au_length * 8) access_unit;
-}
-~~~~
-
-+ au_length
-> indicates the size of an access unit measured in bytes. The size does not include the length field itself.
-
-+ access_unit
-> contains a single access unit. It includes both the 4-characters signature and the variable length encapsulated PBU streams.
+When APV coded bitstream is encapsulated in a track with APVSampleEntry, each sample shall contain one and only one access unit of APV coded data. The format of sample shall be same as the raw_bitstream_access_unit, the length field of four bytes preceeding the access unit data, as defined in the section 12.1 of [APV codec specification](#apv-codec).
 
 ###	Sync sample
 Every samples of APV bitstream shall be sync samples.
@@ -203,12 +190,12 @@ tile_index for sub-samples based on tiles, this parameter indicates the tile ind
 
 # Sub-parameters for the MIME tyype 'codecs' parameter
 
-When the 'codecs' parameter of a MIME type is used for a track containing  APV bistream, as defined in IETF RFC 6381, the sub-parameters defined in this section is used. 
+When the 'codecs' parameter of a MIME type is used for a track containing  APV bistream, as defined in IETF RFC 6381, the sub-parameters defined in this section is used.
 
 The 'codecs' parameter string for the APV bitstream is defined as follows:
 
 ~~~
-<4CC value of sample entry>.<key1><value1>.<key2><value2>.¡¦.<keyN><valueN>
+<4CC value of sample entry>.<key1><value1>.<key2><value2>...<keyN><valueN>
 ~~~
 
 The keys are defined as 4CC values and the value used for each keys are defined in the table below.
@@ -219,4 +206,10 @@ The keys are defined as 4CC values and the value used for each keys are defined
 |'apvl'| level | the largest value of the level_idc in APVDecoderConfigurationRecord |
 |'apvb'| band | the largest value of the band_idc in APVDecoderConfigurationRecord |
 
-For example, codecs="apv1.apvf44.apvl210.apvb3" indicates the track is compliant to 'apv1' sample entry type and the largest value of the profile in APVDecoderConfigurationRecord of the track is 422-12 profile, the level is 7 and the band is 3. 
+For example, codecs="apv1.apvf44.apvl210.apvb3" indicates the track is compliant to 'apv1' sample entry type and the largest value of the profile in APVDecoderConfigurationRecord of the track is 422-12 profile, the level is 7 and the band is 3.
+
+# References
+
+<a name="apv-codec"></a>
++ APV codec
+> The IETF Internet-Draft of APV codec: https://datatracker.ietf.org/doc/html/draft-lim-apv.