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Old 17th January 2021, 11:46   #1  |  Link
Ilbuono
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Encode Dolby Digital Plus Audio (E-AC3)

I have a PCM file (2.0 / 24bit / 2304 kb/s). I want to transcode it to E-AC3 2.0ch (DD+ 2.0). What bitrate should I choose for that E-AC3 file?

I don't have much experience for this, hope to receive your help!
Thanks very much !
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Old 17th January 2021, 15:08   #2  |  Link
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Bandwidth restrictions: How much bitrate can be transmitted ? Give as much bitrate as you can, minus a safety margin.
Quality restrictions: How much degradation of resulting file can be tolerated ? Give as much bitrate as you can.
Media restrictions: What media the resulting file shall be stored upon ? Read up media/container manuals, respect their restrictions.
Player restrictions: On which player the resulting file shall be played ? Read up player's manuals, respect their restrictions.
Filesize restrictions: Running out of space ? Give as low bitrate as you can.
Now you decide about your preferences vs. their priorities.
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Old 17th January 2021, 20:45   #3  |  Link
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@Ilbuono
You are welcome to Doom9 forum.

Maybe you can try 160 Kb/s (good) or 192 Kb/s (near transparent)
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Old 17th January 2021, 21:03   #4  |  Link
microchip8
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For 2 channel audio, I use 320 kbps (160 kbps/channel) for E-AC-3
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Old 19th January 2021, 00:44   #5  |  Link
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160-224kps. For most lossy codecs, they're generally not useful above a certain point imo (for listening purposes).

Last edited by junh1024; 19th January 2021 at 02:14.
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Old 19th January 2021, 11:15   #6  |  Link
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Quote:
Originally Posted by Ilbuono View Post
I have a PCM file (2.0 / 24bit / 2304 kb/s). I want to transcode it to E-AC3 2.0ch (DD+ 2.0). What bitrate should I choose for that E-AC3 file?
For the sake of clarity... Do you want to transcode or encode?
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Old 20th January 2021, 03:40   #7  |  Link
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Which encoder are you using?

The official Dolby encoder should give good quality at or above 128 Kbps. The rule of thumb with vanilla AC-3 was 192 Kbps, so I'd probably either just do that or maybe a hair lower like 160
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Old 20th January 2021, 06:51   #8  |  Link
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Interesting, EAC3 just like DTS's d.c.a. is not limited to a small "finite" set of ready-made bitrates, but most people keep using the well-known values from the old AC3 or/and from the MP3 era anyway
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Old 20th January 2021, 07:23   #9  |  Link
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Many production encoders have a fixed list of supported bitrates. I'm familiar with Dolby Encoding Engine, which lists the following in its documentation:

Code:
32, 40, 48, 56, 64, 72, 80, 88, 96, 104,
112, 120, 128, 144, 160, 176, 192, 200,
208, 216, 224, 232, 240, 248, 256, 272,
288, 304, 320, 336, 352, 368, 384, 400,
448, 512, 576, 640, 704, 768, 832, 896,
960, 1008, 1024,

For mono: 32 (minimum), 1024 (maximum)
Default: 64

For stereo: 96 (minimum), 1024 (maximum)
Default: 128

For 5.1: 192 (minimum), 1024 (maximum)
Default: 192

For 7.1: 384, 448, 504, 576, 640, 704,
768, 832, 896, 960, 1008, 1024
Default: 384
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Old 20th January 2021, 08:03   #10  |  Link
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Quote:
Originally Posted by Blue_MiSfit View Post
Many production encoders have a fixed list of supported bitrates. I'm familiar with Dolby Encoding Engine, which lists the following in its documentation:

Code:
32, 40, 48, 56, 64, 72, 80, 88, 96, 104,
112, 120, 128, 144, 160, 176, 192, 200,
208, 216, 224, 232, 240, 248, 256, 272,
288, 304, 320, 336, 352, 368, 384, 400,
448, 512, 576, 640, 704, 768, 832, 896,
960, 1008, 1024,

For mono: 32 (minimum), 1024 (maximum)
Default: 64

For stereo: 96 (minimum), 1024 (maximum)
Default: 128

For 5.1: 192 (minimum), 1024 (maximum)
Default: 192

For 7.1: 384, 448, 504, 576, 640, 704,
768, 832, 896, 960, 1008, 1024
Default: 384
Many thanks for the useful list *THUMBS UP*
But it sucks that the FOSS encoders may follow the specifications better than the creators of the specifications themselves
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Old 21st January 2021, 04:18   #11  |  Link
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Indeed! It may be just to keep QA cycles tighter

It also probably has roots in broadcast hardware encoders where you wouldn't want to "dial-a-bitrate" one Kbps at a time. You want logical steps since you're tapping a button on chassis or twisting a dial.
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Old 4th February 2021, 10:54   #12  |  Link
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Queueing to this opened topic.

I am thinking about starting to convert all the THD/DTSHD tracks in a movie to EAC3 instead of AC3, as I did since some years so far.

Given I would anyway convert to 5.1 (FFMPEG limitation) and 640 kbps, should I get some benefits or EAC3 has the same algorithms of AC3 plus just the increase in bitrate and channel numbers?

I have been thorougly searching thru the web but no testing has been done AFAIK, especially with FFMPEG instead of commercial encoders.
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Old 4th February 2021, 12:31   #13  |  Link
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Quote:
Originally Posted by tormento View Post
Queueing to this opened topic.

I am thinking about starting to convert all the THD/DTSHD tracks in a movie to EAC3 instead of AC3, as I did since some years so far.

Given I would anyway convert to 5.1 (FFMPEG limitation) and 640 kbps, should I get some benefits or EAC3 has the same algorithms of AC3 plus just the increase in bitrate and channel numbers?

I have been thorougly searching thru the web but no testing has been done AFAIK, especially with FFMPEG instead of commercial encoders.
You will get slightly better quality and AC-3. FFmpeg's implements all algo's that E-AC-3 offers. Channel numbers is still restricted to 5.1 max, though
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Old 4th February 2021, 12:49   #14  |  Link
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Quote:
Originally Posted by microchip8 View Post
FFmpeg's implements all algo's that E-AC-3 offers.
I have tried to find the possible parameters for eac3 but unsuccessfully. Can you help me?

Again, I've read EBU Evaluations of Multichannel Audio Codecs, where DD at 448 kb/s is comparable to DTS at 1.5 mbit/s.

I have read that DD+ is "transparent" to AV receiver, in the way that, if not supported, it is dynamically transcoded to AC3. Is it true?
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Last edited by tormento; 4th February 2021 at 12:52.
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Old 4th February 2021, 13:14   #15  |  Link
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Quote:
Originally Posted by tormento View Post
I have tried to find the possible parameters for eac3 but unsuccessfully. Can you help me?

Again, I've read EBU Evaluations of Multichannel Audio Codecs, where DD at 448 kb/s is comparable to DTS at 1.5 mbit/s.

I have read that DD+ is "transparent" to AV receiver, in the way that, if not supported, it is dynamically transcoded to AC3. Is it true?

There are no parameters for E-AC-3, except for DRC. You just set it like AC-3 and it does its job. With E-AC-3 you can get the same quality but at lower bitrate than AC-3. I personally encode for years to E-AC-3 5.1 (160 kbps/chan) @ 960 kbps for true transparency. I find higher bitrate doesn't improve things

Yes, AVRs that do not support E-AC-3 will on-the-fly transcode it to AC-3. But this depends on the AVR. Some just give an error about not supported audio codec
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Old 4th February 2021, 13:18   #16  |  Link
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Quote:
Originally Posted by microchip8 View Post
Yes, AVRs that do not support E-AC-3 will on-the-fly transcode it to AC-3. But this depends on the AVR. Some just give an error about not supported audio codec
Do you have experience with some brand/model of television and AV receivers that support it or the transcoding option?

Any problem with passthru bitstream thru optical or HDMI?
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Last edited by tormento; 4th February 2021 at 13:20.
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Old 4th February 2021, 13:31   #17  |  Link
microchip8
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Quote:
Originally Posted by tormento View Post
Do you have experience with some brand/model of television and AV receivers that support it or the transcoding option?

Any problem with passthru bitstream thru optical or HDMI?
Yamaha, Denon, Onkyo and Pioneer support E-AC-3 passthrough. With other brands I have no experience. Just check on specs if it supports DD+

While optical can push much higher bitrate audio, virtually all TVs limit it for me unknown reasons. So if you feed a TV that supports DD+ and output it through optical, the TV will transcode it to AC-3

HDMI is dependent on ARC. Most current TVs only support ARC while more and more TVs are coming with eARC which makes it possible to output (compressed) HD audio. My Samsung QLED TV from 2020 supports eARC but my AVR does not. Not a problem since I use an NV Shield + Kodi/VLC that passes over to the AVR so I have no problem with transcoding
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Old 4th February 2021, 13:34   #18  |  Link
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Quote:
Originally Posted by microchip8 View Post
Most current TVs only support ARC while more and more TVs are coming with eARC
So, almost every newer TVs and AVs will accept a passthru by HDMI with no issues, right? I have neither of them but I just want to be sure that what I encode now in EAC3 will be as supported as AC3.
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Old 4th February 2021, 15:05   #19  |  Link
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Quote:
Originally Posted by tormento View Post
So, almost every newer TVs and AVs will accept a passthru by HDMI with no issues, right? I have neither of them but I just want to be sure that what I encode now in EAC3 will be as supported as AC3.
All current major brand AVRs support E-AC-3. If you use a streaming device like NV Shield, the AVRs will happily accept E-AC-3 and pass it on without processing/transcoding

For TVs, you need eARC to pass through E-AC-3. Normal ARC won't do it
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Old 4th February 2021, 15:49   #20  |  Link
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With TrueHD sources, I'd rather snatch the core AC3 track which is the most compatible and high quality in itself.
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