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Old 2nd October 2020, 11:57   #15021  |  Link
tebasuna51
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To view AC3 metadata you can use MediaInfo or my LeeAudBi tool.

I don't know other tool to edit AC3 metadata, only eac3to for set DN to -31dB or specific tools for instance the attached ones:

- DN27_Ac3 restore the Dolby DN default value to -27 dB (a decoder Dolby compliant must attenuate in 4dB the full stream by default)

- DN31_Ac3 remove the DN, setting the value to -31 dB (a decoder must decode without attenuate nothing, recommended for recode in ac3to by default)

- DplAc3 set the Dolby Pro Logic flag in stereo AC3's

I don't know other metadata than can be safely changed without recode.
BTW there are here (now DN work also with EAC3)the sources to do other changes.
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Last edited by tebasuna51; 29th September 2021 at 16:48.
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Old 2nd October 2020, 12:05   #15022  |  Link
NiN3
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Quote:
Originally Posted by tebasuna51 View Post
To view AC3 metadata you can use MediaInfo or my LeeAudBi tool.

I don't know other tool to edit AC3 metadata, only eac3to for set DN to -31dB or specific tools for instance the attached ones:

- DN27_Ac3 restore the Dolby DN default value to -27 dB (a decoder Dolby compliant must attenuate in 4dB the full stream by default)

- DN31_Ac3 remove the DN, setting the value to -31 dB (a decoder must decode without attenuate nothing, recommended for recode in ac3to by default)

- DplAc3 set the Dolby Pro Logic flag in stereo AC3's

I don't know other metadata than can be safely changed without recode.
BTW there are the sources to do other changes.
DRC profiles can't be edited or removed from an AC3 file? I've read dynamic range compression doesn't actually change the soundwaves but is instead saved as metadata for the receiver to decode. Would be interesting if there was a way to remove it from an AC3 or TrueHD stream since most DVD's and Blurays seem to have "Film Standard" applied by default.
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Old 2nd October 2020, 12:46   #15023  |  Link
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Quote:
Originally Posted by NiN3 View Post
DRC profiles can't be edited or removed from an AC3 file? I've read dynamic range compression doesn't actually change the soundwaves but is instead saved as metadata for the receiver to decode....
I can't speak for AC3 audio streams but I've used UsEac3To to remove the dialnorm from DTS audio streams. It worked perfectly with 'Peter Gabriel's - Play' DVD: -

https://forums.stevehoffman.tv/threa...urround.63579/
https://forums.stevehoffman.tv/threa...ls-play.45319/
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Old 2nd October 2020, 12:51   #15024  |  Link
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Quote:
Originally Posted by NiN3 View Post
DRC profiles can't be edited or removed from an AC3 file?
It is difficult because DRC info is provided in audioblocks (6 for each frame) not with common metadata in BSI (Bit Stream Information) header frame info.

All decoders can be instructed to ignore DRC (or apply only a part).
You can recode these ac3 streams with ffmpeg and -drc_scale 0
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Old 2nd October 2020, 17:51   #15025  |  Link
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Thanks for LeeAudBi tool.
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Old 11th October 2020, 17:14   #15026  |  Link
villaquien
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I delayed the audio 400ms but the program copied part of the previous dialog. The silence should start at minute 22:25:780, why does this happen?

https://imgur.com/Vtt9exm.jpg
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Old 11th October 2020, 20:51   #15027  |  Link
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Try with:

-edit=0:22:25.780,400ms -silence
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Old 12th October 2020, 18:32   #15028  |  Link
villaquien
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Thank you. I tried that and the program cuts the last part of the dialogue and moves it forward. I don't understand why the program doesn't create a silence from the exact point.

https://imgur.com/OGOspPl.jpg
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Old 12th October 2020, 20:01   #15029  |  Link
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Seems the cut point is calculated like: 0:22:25.780 -400 = 0:22:25.380

Then to obtain the desired point need:

-edit=0:22:26.180,400ms -silence
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Old 13th October 2020, 18:18   #15030  |  Link
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It worked, thank you.
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Old 17th October 2020, 09:17   #15031  |  Link
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Quote:
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Is eac3to the only software that can remove AC3 dialog normalization?
Thanks
MKVToolNix can remove dialog normalization from AC3 and DTS-HD tracks, from both the master and the embedded core track.

https://gitlab.com/mbunkus/mkvtoolnix/issues/2377
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Old 17th October 2020, 12:13   #15032  |  Link
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MKVToolNix can remove dialog normalization from AC3 and DTS-HD tracks, from both the master and the embedded core track.
All days I learn one more thing.

Yes, in MKVToolNix GUI -> Preferences -> Default values we can "Enable dialog_normalization gain removal for audio tracks"

But maybe the correct text was:
"Enable dialog_normalization attenuation removal for audio tracks"
because enabling the removal we obtain a more loud track.

Remove the Dialog Normalization in a AC3 track means put -31 dB in the field of each header. A standard value is -27 dB than say to decoders dolby compliants attenuate the track by 4 dB (-27-4=-31)
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Last edited by tebasuna51; 20th October 2020 at 12:09. Reason: typo
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Old 20th October 2020, 07:35   #15033  |  Link
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As explained in chapter 6 of this document...
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Old 2nd November 2020, 01:02   #15034  |  Link
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Is there any way to compare two encodes to see if they are identical / "bit perfect" compared to each other? If the same source file is encoded using two different encoders for example.
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Old 2nd November 2020, 01:10   #15035  |  Link
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To compare two files to see if are bit-identical you can use the MSDOS command line:

FC /B file1 file2

(FileCompare /binary)

But, of course, if the files are encodes from different encoders it is improbable obtain the same file.
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Old 2nd November 2020, 01:17   #15036  |  Link
NiN3
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Quote:
Originally Posted by tebasuna51 View Post
To compare two files to see if are bit-identical you can use the MSDOS command line:

FC /B file1 file2

(FileCompare /binary)

But, of course, if the files are encodes from different encoders it is improbable obtain the same file.
Both files were encoded with two different officially "certified" encoders so I am trying to see if there is any difference between them. They are otherwise identical, same exact file size and spectogram.
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Old 2nd November 2020, 08:27   #15037  |  Link
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To compare the decoded video content, you can open both clips in AviSynth and use some comparing functions (Subtract creates a visual difference which you can enhance with Levels, and Compare writes statistics to a CSV file). Also there are video comparing applications (like Fritz Framalyzer). But that does not compare the video bitstreams, which may differ in details (e.g. timestamp values) but still decode to identical videos.

But why do you ask that in a thread about eac3to, which is an audio-only converter?
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Old 2nd November 2020, 10:26   #15038  |  Link
NiN3
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Quote:
Originally Posted by LigH View Post
To compare the decoded video content, you can open both clips in AviSynth and use some comparing functions (Subtract creates a visual difference which you can enhance with Levels, and Compare writes statistics to a CSV file). Also there are video comparing applications (like Fritz Framalyzer). But that does not compare the video bitstreams, which may differ in details (e.g. timestamp values) but still decode to identical videos.

But why do you ask that in a thread about eac3to, which is an audio-only converter?
Audio is what I was asking about.
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Old 2nd November 2020, 10:59   #15039  |  Link
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Oh, then I misunderstood, sorry ... but in one regard, the same applies to audio just as to video: Files may have slight differences in metadata, even widely different compressed bitstreams (depends on the used audio format and its encoding algorithm), yet would produce identical decoded results.

Audacity seems to have a CompareAudio function for two tracks. Or you can use the hash muxer in ffmpeg (note that it would return different hashes if compressed audio uses block lengths and the number of samples differs).
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Old 9th November 2020, 14:31   #15040  |  Link
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When decoding TrueHD 7.1 with libav/ffmpeg I get this message "Lossless check failed - expected 00, calculated fd". Anything to worry about? It does seem to output 8 channels correctly.
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