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17th January 2021, 11:46 | #1 | Link |
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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 ! |
17th January 2021, 15:08 | #2 | Link |
Big Bit Savings Now !
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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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19th January 2021, 11:15 | #6 | Link |
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For the sake of clarity... Do you want to transcode or encode?
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20th January 2021, 03:40 | #7 | Link |
Derek Prestegard IRL
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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 |
20th January 2021, 06:51 | #8 | Link |
SuperVirus
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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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20th January 2021, 07:23 | #9 | Link |
Derek Prestegard IRL
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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 |
20th January 2021, 08:03 | #10 | Link | |
SuperVirus
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Quote:
But it sucks that the FOSS encoders may follow the specifications better than the creators of the specifications themselves |
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21st January 2021, 04:18 | #11 | Link |
Derek Prestegard IRL
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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. |
4th February 2021, 10:54 | #12 | Link |
Acid fr0g
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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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4th February 2021, 12:31 | #13 | Link | |
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Quote:
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4th February 2021, 12:49 | #14 | Link |
Acid fr0g
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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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4th February 2021, 13:14 | #15 | Link | |
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Quote:
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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4th February 2021, 13:18 | #16 | Link | |
Acid fr0g
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Quote:
Any problem with passthru bitstream thru optical or HDMI?
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4th February 2021, 13:31 | #17 | Link | |
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Quote:
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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4th February 2021, 13:34 | #18 | Link |
Acid fr0g
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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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4th February 2021, 15:05 | #19 | Link | |
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Quote:
For TVs, you need eARC to pass through E-AC-3. Normal ARC won't do it |
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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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