[FFmpeg-devel] [PATCH] mp4 and ipod metadata

Baptiste Coudurier baptiste.coudurier
Sun Jun 15 00:12:49 CEST 2008

Michael Niedermayer wrote:
> On Fri, Jun 13, 2008 at 09:14:13PM -0700, Baptiste Coudurier wrote:
>> Michael Niedermayer wrote:
>>> On Fri, Jun 13, 2008 at 02:26:24PM -0700, Baptiste Coudurier
>>> wrote:
>>>> Baptiste Coudurier wrote:
>>>>> Michael Niedermayer wrote:
>>>>>>>> [...]
>>>>>>>> And above all even if no spec defined it, that would
>>>>>>>> not affect that its default value of 2 would be valid
>>>>>>>> for all specs then (as none defined it otherwise). Its
>>>>>>>> kinda simple either one defines it or none defines it.
>>>>>>>> Either way there the incompatibility you claimed does
>>>>>>>> not exist. Whats even more ridiculous is that you
>>>>>>>> insist to only support a ancient revission of the 3gp
>>>>>>>> spec because the later REQUIRE all 3gp files to claim
>>>>>>>> to be iso media compatible. And you seem to prefer if
>>>>>>>> they are not compatible.
>>>>>>> This is false.
>>>>>> what is false?
>>>>> That I insist to only support an ancient revision. I dont
>>>>> prefer them not being compatible, I'm definitely ok to put
>>>>> 'isom' in compatible brands, and as much compatible brands
>>>>> that it is possible.
>>>> Here is an attempt, I may have overlooked things.
>>> This patch changes quite a lot of things at the same time ...
>> Yes. I'll split the commits.
>>>> +        if (codec_get_tag(codec_3gp_tags,
>>>> st->codec->codec_id)) +            has_3gp_tags |= 1<<i;
>>> will fail with >32 streams
>> Damn. Ok.

Changed the logic.

> [...]
>> Also:
>> "5.5	File-branding guidelines
>> [...]
>> -	that a reader implementing that specification (possibly only that
>>  specification) is given permission to read and interpret the
>> file."
>> If we put codecs not supported, the reader will not be given
>> permission to read the file IMHO.
>> "All 3GP files of Release 5 or later shall contain the compatible
>> brand ?isom? indicating that they conform to the ISO base media
>> file format, unless the reader is required to interpret extensions
>> specific to the AVC file format [20], for which case the compatible
>> brand ?avc1? shall be used instead (see note 2)"
>> Seems if we want to force the player to be able read H.264 track it
>>  seems with must not put "isom". Do we want ? He might still read
>> the audio track.
> hmm, i would vote for leaving isom in there being able to listen to
> the audio of a music video is nice by itself.

Yeah I agree.

I reversed the condition for psp and for mov since I thought it was
similar. This is the patch I'd like to have applied at the end.

Tell me if you want another pretty printing code.

And, again, I found something with the minor version in 3gp/3g2:

"MinorVersion: This identifies the minor version of the brand. Files
with brand '3g2x', where x is an alphabetic character, shall have a
corresponding release X.Y.Z such that X = 1 when x = 'a'; X = 2 when x =
'b'; and so on. A conforming minor version value for releaseX.y.z uses
the byte aligned and right adjusted value of release X*2562 + y*256+z."

While for 3gp is:
"MinorVersion:  This identifies the minor version of the brand.  For
files with brand '3gLZ', where L is a letter and Z a digit, and
conforming to version Z.x.y of this specification, this field takes the
value x*256 + y."

First 3gp standard defining the use of brand and defining specific 3gp
file format was 4.2.0 (TS 26.234 4.2.0), this explains 0x200.

3gp6 we can use 6.0.0, therefore 0 as minor.

Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
Smartjog USA Inc.                                http://www.smartjog.com
Key fingerprint                 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA
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