On Mon, Apr 02, 2018 at 12:02:38PM +0300, Timo Teras wrote: > On Fri, 30 Mar 2018 04:06:03 +0300 > Timo Teras <timo.te...@iki.fi> wrote: > > > On Fri, 30 Mar 2018 02:39:13 +0200 > > Michael Niedermayer <mich...@niedermayer.cc> wrote: > > > > > git log points to > > > bed4fc54c947b9e36d2103b400d438bfb4dd80dd > > > > > > This commit added both cpy and cprt, that makes your hypothesis not > > > fit very well > > > > That commit adds it to three places: > > - MOV mode which is basically in mov_write_udta_tag() using '\251cpy' > > which published in Apple docs > > - 3GP mode using 'cprt' which is in ISO standard > > - mov_write_ilst_tag() is iTunes which is non-documented > > > > The commit adds exactly one tag to each variant. To me my hyptothesis > > still looks correct. > > I was thinking and researching this more. It looks like: > - 3GP defines 'cprt' which is completely different encoding and > appears under different atom > - \251cpy is the QuickTime atom documented by Apple > - but it seems iTunes uses and has always used undocumented 'cprt' > which similar to other iTunes atoms > > It seems that other software supporting iTunes support 'cprt' format. > There are few other things that support also '\251cpy' variant in this > context, but they are few. > > Now I suspect ffmpeg started writing '\251cpy' atoms also for the > iTunes tag based on the assumption that the tag there would follow > QuickTime format as many other iTunes tags follow. > > And this almost sounds like any other software supporting '\251cpy' > here do it to support ffmpeg encoded incorrect streams. > > My preference on fixing this is as follows: > 1. Just change '\251cpy' to 'cprt' as this seems to be the canonical > atom > 2. My previously suggested patch. Write 'cprt' by default, but have > flag to write the other tag > 3. Write both by default, but add flag to suppress the '\251cpy' atom > > Suggestions and additional input welcome.
if there is no reply from anyone providing more information than the choice you prefer (1.) should be ok thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB If you drop bombs on a foreign country and kill a hundred thousand innocent people, expect your government to call the consequence "unprovoked inhuman terrorist attacks" and use it to justify dropping more bombs and killing more people. The technology changed, the idea is old.
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