Add AC3 Atom support to MP4Info and MP4Dump

[GnaphronG]

MP4Info doesn't return the info of AC-3 tracks:
For example using the AC-3 file for the HLS Advanced stream example https://developer.apple.com/streaming/examples/:
https://tungsten.aaplimg.com/VOD/bipbop_adv_fmp4_example/a2/main.mp4

$ mp4info main.mp4
...
  Sample Description 0
    Coding:      ac-3 (Dolby Digital (AC-3))
    Sample Rate: 48000
    Sample Size: 16
    Channels:    2
...

The patch returns results similar to EC-3 tracks for AC-3 tracks

$ mp4info main.mp4
...
Sample Description 0
    Coding:      ac-3 (Dolby Digital (AC-3))
    Sample Rate: 48000
    Sample Size: 16
    Channels:    2
    AC3 stream:
        fscod       = 0
        bsid        = 6
        bsmod       = 0
        acmod       = 7
        lfeon       = 1
        bit_rate_code = 10
    AC3 dac3 payload: [0c3d40]
...

[nadimix]

Thanks @GnaphronG! This would be really helpful 👍

[essolsoj]

If you want to support encrypted audio tracks, you could do so by changing this line to the following:
if (GetContext() == AP4_ATOM_TYPE_AC_3 || GetContext() == AP4_ATOM_TYPE_ENCA) {

[barbibulle]

This fix is included in the current master branch on GitHub.

…

On Wed, Aug 16, 2017 at 8:58 AM, essolsoj ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In Source/C++/Core/Ap4AtomFactory.cpp <#122 (comment)> : > @@ -711,6 +712,13 @@ AP4_AtomFactory::CreateAtomFromStream(AP4_ByteStream& stream, atom = AP4_Dec3Atom::Create(size_32, stream); } break; + case AP4_ATOM_TYPE_DAC3: + if (atom_is_large) return AP4_ERROR_INVALID_FORMAT; + if (GetContext() == AP4_ATOM_TYPE_AC_3) { If you want to support encrypted audio tracks, you could do so by changing this line to the following: if (GetContext() == AP4_ATOM_TYPE_AC_3 || GetContext() == AP4_ATOM_TYPE_ENCA) { — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#122 (review)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ACWJjTOOA7wANN5qFxJytwk2lJ2N8AI6ks5sYxGfgaJpZM4Le_9j> .

[svart-riddare]

Wouldn't we want a payload of at least 3 bytes (as we read payload[2] line 86) ?

[barbibulle]

You're right, this should be < 3

[svart-riddare]

payload[0] << 2 is meaningless as the line ends with & 0x3. Perhaps we want & 0x7 ?

[barbibulle]

Good catch. This should be masked with 0x7, not 0x3, as the field is 3 bits wide. Thanks for spotting that.