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axiomatic-systems / Bento4

Full-featured MP4 format, MPEG DASH, HLS, CMAF SDK and tools
http://www.bento4.com
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About loudness atom 'ludt' #753

Open xinyuwang-hotstar opened 2 years ago

xinyuwang-hotstar commented 2 years ago

Hi team,

We found in the Apple HLS spec, https://developer.apple.com/documentation/http_live_streaming/http_live_streaming_hls_authoring_specification_for_apple_devices There is a statement regarding ludt:

2.19. In fMP4 files, you SHOULD provide loudness information by way of a loudness box ('ludt'). When present, the loudness box takes precedence over any loudness information in the audio stream.

But seems Bento4 doesn't support ludt yet. I tried to dump atoms of a xHE-AAC encoded mp4 file with mp4dump, but didn't find ludt.

So does Bento4 support ludt? If yes, could you share an example mp4 file with ludt data?

Thanks!

barbibulle commented 1 year ago

Could you provide a link to an example file with a ludt box?

xinyuwang-hotstar commented 1 year ago

@barbibulle Here is a mp4 file shared by MPEG/Apple team. But seems that is not compatible with their parsing code. https://github.com/MPEGGroup/isobmff/issues/38#issuecomment-1245960744