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18th June 2011, 06:10 | #1 | Link |
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(E-)AC3 decoders comparison
I did some comparison of (E-)AC3 decoders, may be it will be useful.
I. E-AC3 decoders comparison. Arrangement: Code:
Encoding WAV (PCM) to E-AC3 — Dolby® Media Encoder SE v1.3.8 (from Dolby Media Producer Suite). Preprocessing was disabled, DRC="none", DN=-31dB, target="Standard". Screens of settings. Decoding E-AC3 to WAV (PCM): Code:
I. Scheme 2.0. Source test1.wav (stereo) was encoded to E-AC3 1536 kbps and then was decoded. Download all streams. 1). Frequency response of libavcodec is the same as frequency response of licensed decoders (ArcSoft, Sonic, Nero and Cyberlink). 2). In some cases libavcodec provides too low SNR for some of the channels. These differences may be significant. Very strange for a predetermined process (bug?). 3). In some cases SNR (libav-eac3to) little more than SNR (libav-ffmpeg). Most likely because libav in eac3to was patched by madshi for decoding to 24-bit (against 16-bit for libav-ffmpeg). As libavcodec is the only decoder that can ignore DRC [Madshi unable to completely disable the use of DRC in eac3to-Nero. I can confirm it for E-AC3], it would be nice to get rid of the trouble with SNR. Licensed decoders use the DRC and therefore can not be used for properly decoding, because all the corporate tracks E-AC3 are encoded with DRC (Dolby's recommendation). Last edited by TDiTP_; 25th June 2011 at 15:46. Reason: typo |
18th June 2011, 08:45 | #2 | Link |
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II. AC3 decoders comparison.
Arrangement: Code:
Encoding WAV (PCM) to AC3 — DolbyEncoder (SFSE 1.0). Preprocessing was disabled, DRC="none", DN=-31dB. Decoding AC3 to WAV (PCM): Code:
I. Scheme 1.0. Two different samples were encoded to AC3 96kbps and then were decoded. Source t2.wav was obtained from source t1.wav through the low-pass filter (16kHz). Download test1, Download test2. Tested decoders can be divided into two groups: "A" - liba52, azid, sfse, cyberlink. "B" - libav, nero7, nero9, sonic, arcsoft. UPD: internal decoder of "SurCode for Dolby Digital® 5.1 Encoder and Decoder" was tested. It's belongs to "B". 1). Frequency response of "A" is closer to source than frequency response of "B" (downturn of high frequencies, usually after 13-17 kHz). It's very strange for a predetermined process! 2). There are differences in SNR between decoders (and between groups) but in general they can be considered negligible (i think). Last edited by tebasuna51; 7th December 2012 at 09:04. |
18th June 2011, 18:51 | #3 | Link | |
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Quote:
Also, the internal representation vs. the output sample format (and the conversion process) could be different for the decoders. For example, some decoders may use a 16-bit or 24-bit fixed point representation in the decoder, while others may use floating-point then convert to 24-bit. |
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18th June 2011, 18:59 | #4 | Link | |
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Also, as of a few months ago, Libav can output 24-bit AC-3 and E-AC-3. example: Code:
ffmpeg -i test.ac3 -drc_scale 0 -acodec pcm_s24le -y test.wav Last edited by jruggle; 18th June 2011 at 19:04. Reason: added link to win32 builds |
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18th June 2011, 19:56 | #5 | Link | |||
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Quote:
Quote:
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UPD. If you need more samples of E-AC3, let me know. Last edited by TDiTP_; 18th June 2011 at 21:23. |
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16th January 2012, 01:06 | #6 | Link |
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Based on these findings, is it not worth messing with Nero 7 in EAC3to for decoding ac3? I tracked down a copy of Nero 7 based on eac3to's recommendation for using Nero Audio Decoder, however, my eac3to is still not seeing Nero 7 when I run:
> eac3to -test I am wondering if it is even worth troubleshooting why this is if libav is just as capable (or maybe even better if it can ignore DRC)??? |
16th January 2012, 05:51 | #7 | Link |
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I personally never bothered to install Nero 7 for eac3to. What for? Decoding AC3? I've reencoded plethora of DVD or BD files via eac3to:libav and I've yet to find any problem with AC3 -> AAC conversion...
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19th January 2012, 10:11 | #10 | Link | |
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You do. I did. Still not working. I am going to uninstall nero 7 which is useless for me other than that codec I wanted for eac3to. I agree that libav is fine for ac3 decoding, and I have better programs for doing ac3 encoding. |
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5th January 2013, 12:32 | #11 | Link | ||
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Quote:
Quote:
https://bugzilla.libav.org/show_bug.cgi?id=415 |
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15th October 2014, 07:42 | #12 | Link |
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EAC3-Decoding
It doesn't look like a "feature" that the libav decoder is missing. Instead it seems to me that one of the E-AC3 frames is decoded totally wrong, which reduces the SNR value that much. 99% of the file are decoded with the same quality as the Nero decoder. It's just a few milliseconds that are somewhat damaged. I've created a Bugzilla bug report for this here:
https://bugzilla.libav.org/show_bug.cgi?id=415[/QUOTE] Is that really a problem or is the bug inaudible? Thanks |
15th October 2014, 13:16 | #13 | Link |
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Actually, Adobe Audition CC 2014.1 decode ac3, I think that properly. Could be updated these tests with that soft???
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20th May 2018, 10:30 | #15 | Link |
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CyberLink. DirectShow's graph: "LAV Splitter → CyberLink Audio Decoder (PDVD10) → Wav Dest → File Writer" was built in GraphEdit. Decoder is taken from "PowerDVD 10 Mark II 10.0.2701.51". Output is represented in 16-bit int.
I could not turn off the forced mixing to 2.0 inside DS-filter. How to use CyberLink Audio Decoder (PDVD10) to mono wav? |
25th May 2018, 02:27 | #16 | Link | |
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25th May 2018, 08:27 | #17 | Link |
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Without force -drc_scale 0 the decoder must obey the header field Dialogue normalization.
If Dialogue normalization is -27 dB (many times according to Dolby specs) all channels volume are attenuated by 4 dB. If Dialogue normalization is -31 dB (like free encoders set by default, or eac3to change) -drc_scale 0 is not needed.
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