how to find so many MP4 formats

[manchesterunite]

I'm studying MP4 demux code, and find that there are so many special cases handled in mp4.c.
after looking through ISOIEC14496 specs and APPLE's qtfileformat , I still cannot figure out some cases.

for example:

.....
if( !p_enda )
p_enda = MP4_BoxGet( p_sample, "enda" );

if( p_track->fmt.i_cat == AUDIO_ES && ( p_track->i_sample_size == 1 || p_track->i_sample_size == 2 ) ) // why sample_size=1 or 2 means something, where defines this situation???
{
.......

can anybody help me? tks!

[Rémi Denis-Courmont]

It's unlikely that whomever wrote that piece of code at some point in the past is both going to see your post and remember what exactly this does. You'd better read the file history in the version control.

[manchesterunite]

tks for your replay

I just expect someone who understand the code happened to come here.
whatever...

[Jean-Baptiste Kempf]

Use git blame to find who and why.

[Sébastien Escudier]

http://linux.die.net/man/1/git-blame