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Nevcairiel / LAVFilters

LAV Filters - Open-Source DirectShow Media Splitter and Decoders
GNU General Public License v2.0
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AC4 audio Dolby codec is missing #411

Open jdavlcba opened 3 years ago

jdavlcba commented 3 years ago

Hi guys,

it seems now AC4 is needed in LAVFilters as it is the audio codec that will be used next in French Digital Terrestrial TV with UHD video.

I have stored some test streams broadcast currently from Eiffel tower, to this location: complete transport stream http://lcba.free.fr/UHD_FR/test_UHD_C24_210328_1.ts

partial transport stream with only one service http://lcba.free.fr/UHD_FR/Test%20UHD3%202021-03-28%2003-14-10.ts http://lcba.free.fr/UHD_FR/Test%20UHD3%202021-03-28%2003-10-49.ts http://lcba.free.fr/UHD_FR/Test%20UHD2%202021-03-28%2003-13-18.ts

thanks to take a look.

clsid2 commented 3 years ago

A decoder for AC4 is still in development for FFmpeg. Once it is done and gets added to FFmpeg, which is used by LAV, then it will eventually be available in LAV as well.

jdavlcba commented 3 years ago

Thanks for your feedback !

wiyosaya commented 7 months ago

I'm a MediaPortal user (which uses LAV Filters) who is interested in having AC4 audo support in LAV Filters so that MediaPortal will support ATSC 3.0 OTA TV tuners. As I understand it, ffmpeg needs to work with AC4 for LAV Filters to detect and decode AC4 audio.

It is my understanding that AC4 audio is now supported in the latest build of ffmpeg. Please see the end of the comments in this link. https://trac.ffmpeg.org/ticket/8349

If everything for LAV Filters to detect and decode AC4 audio is now in place, please consider adding AC4 support to LAV Filters. Thank you.

Nevcairiel commented 7 months ago

AC4 is not part of FFmpeg yet. If it would be, LAV support would be almost automatic.

wiyosaya commented 4 months ago

I'm attaching the latest "Readme" from ffmpeg. Please note that under "enabled demuxers" AC4 is listed. Thank you. README.txt

clsid2 commented 4 months ago

Demuxer is not a decoder.

wiyosaya commented 4 months ago

Maybe not, but the thing is that if the demuxer can somehow be used to bitstream the AC4 stream to an HDMI output, then those of us with HTRs that are capable of decoding AC4 can then use our HTRs to decode the stream. I bitstream DTS-HD master audio, and while FFmepeg does not, apparently, decode that either, I do see an entry for it in the dumuxers section of those release notes. Maybe I'm wrong, but it would seem that the demuxer is key in being able to bitstream that format to HDMI which my HTR then decodes.

This is a show-stopping stumbling block for those of us in the US (and anyone else in the world) that would like to add ATSC 3.0 tuners to our HTPC systems. The default audio format for ATSC 3.0 is AC4. With no support for AC4, media software, such as MediaPortal that uses LAV Filters, refuses to recognize ATSC 3.0 stations when discovered/tuned by ATSC 3.0 tuners.

Thanks.