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Old 17th July 2021, 11:33   #1  |  Link
Jerry^
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Sound problem : creaks with AC3 compression

Hello,

Strange .. problems often hide other ones.

Now, when I use audio conversion (to AC3), I have a lot of creaks.

AC3 to AC3 > creaks.
DTS to AC3 > creaks.

If I check "do not reencode AC3", no creaks anymore is the source is AC3.

Somebody could help me ?

NB : I want to convert DTS to AC3.
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Old 17th July 2021, 15:28   #2  |  Link
ggtop
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Hi Jerry,

I do remember I had an issue with cracklingg AC3 audio looong ago (must be 8 years or more) before I had a BR burner I tried some conversions BR down to DVD-5/9 reencoding audio to AC3. If I remember correctly it was a 3 disc edition of Foo Fighters 'Sonic Highway'. Output to BR without touching the audio at all fixed it.

What is xour source and what is your target format?
BDRB uses aften & nicaudio for AC3 conversion and that is what I can say rock stable.

I would suggest to run delaycut on the extracted dts audio file and see if there are any glitches in the stream. I think TSmuxer is also able to report "audio packets not synchronized" errors when outputting to a new structure.

Good luck,
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Last edited by ggtop; 17th July 2021 at 15:31.
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Old 17th July 2021, 22:30   #3  |  Link
tebasuna51
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Quote:
Originally Posted by ggtop View Post
BDRB uses aften & nicaudio for AC3 conversion and that is what I can say rock stable.
The aften encoder is deprecated.

The AC3 encoder recommended is ffmpeg.
The conversión from DTS to AC3 with ffmpeg is direct, we don't need the NicAudio decoder.
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Last edited by tebasuna51; 17th July 2021 at 22:37.
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Old 18th July 2021, 20:37   #4  |  Link
Jerry^
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Quote:
Originally Posted by tebasuna51 View Post
The [URL="https://forum.doom9.org/showthread.php?p=1794293#post1794293"]
The conversión from DTS to AC3 with ffmpeg is direct, we don't need the NicAudio decoder.

Hello, tebasuna51 ;

That's strange ... My log file say ffmeg was used :

Quote:
- Target BD size: 8,89 GB
- Windows Version: 6.2 [9200]
- MOVIE-ONLY mode enabled
- Quality: High Quality (Default), Two Pass
- UHD-BD source detected.
- Decoding/Frame serving: FFMPEG
- Audio Settings: AC3=0 DTS=1 HD=0 Kbs=640
[18:43:42] PHASE ONE, Encoding
- [18:43:42] Processing: VID_00006 (1 of 3)
- [18:43:42] Extracting A/V streams [VID_00006]
- [18:53:28] Reencoding video [VID_00006]
- Source Video: HEVC, 3840x2160
- Rate/Length: 23,976fps, 312 frames
- Bitrate: 5*787 Kbs
- [18:53:28] Reencoding: VID_00006, Pass 1 of 2
- [18:53:56] Reencoding: VID_00006, Pass 2 of 2
- [18:54:19] Video Encode complete
- [18:54:19] Processing audio tracks
- Track 4354 (fra): Reencoding audio to AC3...

Do you have an idea ?

Thanks in advance.
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Old 18th July 2021, 22:53   #5  |  Link
tebasuna51
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Quote:
Originally Posted by Jerry^ View Post
Do you have an idea ?
Sorry, I don't know the audio process of BD Rebuilder.

The log say:
- Track 4354 (fra): Reencoding audio to AC3...

The problem may occur when extract the track 4354:
maybe a old DGIndex or TsMuxeR with problems with multi-m2ts BD

But if you say than preserving the original track is ok, and AC3 -> AC3 creaks only the encoder must be the culprit.
Maybe the old Aften. (FFMPEG seems used for Decoding/Frame serving, not for AC3 encode)

Played in the PC also creaks, or only in BD/DVD hardware player?
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Last edited by tebasuna51; 18th July 2021 at 23:02.
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Old 19th July 2021, 18:13   #6  |  Link
ggtop
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Quote:
Originally Posted by Jerry^ View Post
Do you have an idea ?
Looking at your log it seems you only want to recode the audio as the video part is done in a few seconds. There will likely be other methods to achieve that...
But I suggest you compare the extracted dts and the resulting ac3 for creaks first and try other methods to recode the audio only with other methods (e.g. ffmpeg) to see if that fixes the issue.

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Old 22nd July 2021, 16:33   #7  |  Link
ggtop
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Quote:
Originally Posted by tebasuna51 View Post
The aften encoder is deprecated.

The AC3 encoder recommended is ffmpeg.
The conversión from DTS to AC3 with ffmpeg is direct, we don't need the NicAudio decoder.
Hi tebasuna,

I just changed my workflow to use ffmpeg for DTS>AC3 conversion. Thank you for the input.

Out of interest: Do you also recommend from your experience to use ffmpeg for AC3@640 > AC3@448 conversions or are there more preferred methods?

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Old 22nd July 2021, 23:10   #8  |  Link
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Originally Posted by ggtop View Post
Do you also recommend from your experience to use ffmpeg for AC3@640 > AC3@448 conversions or are there more preferred methods?
If you want save some space lossing quality is ok.
But if your player method support AAC 5.1 or EAC3 it is always better (in that order)
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Old Today, 14:21   #9  |  Link
jdobbs
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I just want to step in here with a bit of reality. The AC3 standard has not changed significantly in a long time, except for extensions (like EAC3). So if you are reencoding to standard AC3 -- it is very unlikely you will detect a difference between an AC3 encode done with AFTEN and one done with FFMPEG. True, AFTEN is no longer developed... but that doesn't change the fact that it is a very good AC3 encoder (notes in tebasuna51's link excepted).

If you are getting "creaks" (whatever that is), it is very unlikely it is coming from the AFTEN encoder. It is highly likely it has some other origin.

That doesn't mean I disagree that FFMPEG is probably a better route to go today for audio encoding for various reasons (like it's ability to decode from many different sources). Just the fact that it is continually updated is a big plus.

Just my humble opinion.
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Last edited by jdobbs; Today at 14:32.
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