AC3 to MP4-AAC

[Sem]

im using MeGUI to convert a dvd into a mp4 for playback on my ps3

the ac3 demuxed from the dvd has a bitrate of 448kpbs
and even when i convert it to a AAC file of equal constant bitrate the mp4 sound is significantly worse than the original ac3 file

whats the best setting to use to get it to sound just as good


thanks

[Blue_MiSfit]

whats the best setting to use to get it to sound just as good


You can't :)

AC3 -> AAC will never sound as good as the original. AAC throws a lot away.

It's pretty good, but from the sound (ha ha ha) of it, you have sensitive ears - like me.

Your best bet is to use LC-AAC (if you aren't already), the Nero encoder, and adaptive bitrate.

Stay away fro HE-AAC as it uses spectral band replication to reproduce high frequencies. Evil!

~MiSfit

[Avenger007]

to sound just as good
Try Variable Bitrate with Q=1. Although Q=0.7 is good enough for me for movies.

[skromnibog]

Stay away fro HE-AAC as it uses spectral band replication to reproduce high frequencies. Evil!

Concluding from the thing that HE sounds bad to you that it is evil and that everybody should stay away from it is very very WRONG.
Public listening tests have shown that Nero's implementation of HE AAC at ~64kbps is good enough for most people and for some people even transparent in most cases. Of course everybody should test it himself and decide whether HE is ok for him/her or not.
One also must have in mind that there were some issues with Nero AAC Encoder for multichannel and that fixes will be available in the next release.

[Avenger007]

@skromnibog
Is there a difference in sound quality between choosing HE-AAC 64kbps adaptive bitrate compared with Q=x variable bitrate, where x gives a bitrate as close to 64kbps as possible?
Sometimes when encoding a long movie at low bitrate I would use Q=0.3.

[Sem]

i tried changing the Variable bitrate to Q=0.7 and the output file ends up larger than the source with no improvement in sound

im just going to carry on with the adaptive bitrate or variable Q=0.5 and leave it at that

i guess if i want to play it on my ps3 i need to compromise

[skromnibog]

Is there a difference in sound quality between choosing HE-AAC 64kbps adaptive bitrate compared with Q=x variable bitrate, where x gives a bitrate as close to 64kbps as possible?
Sometimes when encoding a long movie at low bitrate I would use Q=0.3.
To achieve target bitrate use 'target bitrate mode' specifying desired bitrate, to achieve best quality/size ratio use 'target quality mode' specifying desired q between 0 and 1. It is up to every individual to find out which q value is good enough for him/her.

i tried changing the Variable bitrate to Q=0.7 and the output file ends up larger than the source with no improvement in sound
You can never expect improvement in the sound quality after encoding or re-encoding. The best that can be achieved is that you don't hear any difference compared to the sample that you started with.

[Sem]

what does the Q=0 to 1 mean exactly

what does it change

[skromnibog]

Here is the link to Nero AAC Encoder recommended settings:
http://www.hydrogenaudio.org/forums/index.php?showtopic=44310
There is also explanation of q values.

[tebasuna51]

Here is the link to Nero AAC Encoder recommended settings:
http://www.hydrogenaudio.org/forums/index.php?showtopic=44310
There is also explanation of q values.
The "Approx. average bitrate <-> Quality table" is this thread is for stereo samples.

For 5.1 (448 Kb/s ac3) the equivalent bitrates are greater (maybe x 2.5).

The better choice is maintain the original ac3 (transcode is always worse).
If you want decrease the size use values between q=0.25 to 0.4.
If you need aac format with minimum loss for 448 Kb/s ac3 is enough q=0.5.
Of course this is always average values and can vary with a concrete source.

[Sem]

sorry to be a dumb newb but i just don't get something

448kbps AC3 to AAC

VBR Q=0.5 then selecting 192kbps on the bitrate calculator

the output file is always larger than the source (284Mb to 350Mb)

i dont get it i thought AAC is just like mp3 (smaller file size comparable sound)

what am i doing wrong

thanks :(

[tebasuna51]

448kbps AC3 to AAC
VBR Q=0.5 then selecting 192kbps on the bitrate calculator

If you want a bitrate near to 192 Kb/s for a 5.1 (6 chan) you want 32 Kb/s per channel, then you need Q=0.25 (63 Kb/s for stereo, 2 channels)

the output file is always larger than the source (284Mb to 350Mb)

Of course, is 552 Kb/s or 92 Kb/s per channel (184 Kb/s stereo equivalent)

i dont get it i thought AAC is just like mp3 (smaller file size comparable sound)

what am i doing wrong?

Use Q between 0.25 and 0.4, like I say you in my precedent post.
With Q=0.5 you always obtain a file greater than original ac3.

[Sem]

ok thanks
but what do you think is better using variable or adaptive bitrate

[tebasuna51]

Variable bitrate.

To use ABR is recommended uncompress the ac3 file to wav (phisical big file) and use the -2pass mode with command line parameters. MeGUI/BeHappy/Bepipe/Wavi/SoundOut Avisynth methods can't use the -2pass mode.

[Sem]

Well ive been experimenting and it seems Q=0.35 (AAC-LC) is the sweet spot

as for the quality i think the main thing i am noticing is the volume level

the AC3 file is alot louder than the AAC file and in MeGUI ive ticked the "increase volume automatically" but its still alot lower

is there anything i can do or is that just the nature of transcoding AC3->AAC

also i have another dvd with DTS sound

should i still use the Q=0.3 value or should i experiment again

thanks

[Irakli]

the AC3 file is alot louder than the AAC file and in MeGUI ive ticked the "increase volume automatically" but its still alot lower

I had the same problem before. Checking 'Force Decoding via DirectShow' solves the problem for me (using FFDshow as decoder).

Regards,
Irakli

[Sem]

I had the same problem before. Checking 'Force Decoding via DirectShow' solves the problem for me (using FFDshow as decoder).

Regards,
Irakli

thanks for the tip

gave it a try and it did solve the volume problem but now the output is only 2.0 instead of 5.1

[Sem]

is there another more fully featured audio encoder i could use and only use megui for video and muxing

[Irakli]

thanks for the tip

gave it a try and it did solve the volume problem but now the output is only 2.0 instead of 5.1

Oh, sorry. I forgot to mention that you need to choose 5.1 channel output in FFDshow audio decoder configuration (it's in the 'Mixer' category; 'Output speaker configuration' should be set to '3/2/1 - 6 channels').

I hope this will help.

Edit:

is there another more fully featured audio encoder i could use and only use megui for video and muxing

You could try using BeHappy (it can encode with Nero AAC as well).

Regards,
Irakli

[Sem]

thanks for the help

i changed the output to 5.1 on ffdshow but its still the same

is nero the best aac encoder

ive been trying belight and it has winamp and faac encoders

think id have better luck with them?
thanks

[Irakli]

thanks for the help

i changed the output to 5.1 on ffdshow but its still the same

is nero the best aac encoder

ive been trying belight and it has winamp and faac encoders

think id have better luck with them?
thanks

Yes, in terms of sound quality Winamp AAC is good encoder as well.

As for FAAC, I would stay away from it as sound quality it produces is considerably worse compared to Winamp or Nero AAC.

Regards,
Irakli

[tebasuna51]

MeGUI, BeHappy, BeLight, ...

You can obtain the same results with any, if you select the same settings.

- When you decode ac3 don't aply neither DialogNormalization nor DynamiRangeCompression. With ffdshow you can't unselect DN then you have always low volume. Never use DirectShowSource to decode ac3. With NicAc3Source decoder (MeGUI/BeHappy) the DN is not aplied and DRC can be selected.
The Azid ac3 decoder (BeLight-BeSweet) have also checkboxes for these important parameters. Warning BeLight default is apply DRC.

- When you encode you can use use NeroAacEnc or CT (winamp) encoder in MeGUI or BeHappy or BeLight. The Faac encoder is not recomended. With CT encoder you only can use CBR.

The output volume is the same in ac3 than encoded aac (DN and DRC off, without 'Increase volume', 'maximize', 'normalize', 'ota', 'bost' or other volume changes) no mather the decoder or encoder selected (more or less). If you listen different volume then you need adjust your player, don't search the problem in the transcode process.

[Sem]

well i tired Belight and unticked the box for DRC and disabled the pregain/postgain but no change

the problem is not my player its the file im 100% sure of this

im using MPC and VLC with volume at max

[tebasuna51]

If you are 100% sure, please upload a sample (the ac3 source and the aac/mp4 obtained) to check the problem.

Your players can have different settings depending of input formats, not only the volume button affect.

[Sem]

ok here are the samples

AC3 5.1 448kbps
AAC-LC 5.1 300kbps (Q=0.35)

first 5 mins

the DVD is Futurama benders big score

http://rapidshare.com/files/111735374/VIDEO_TS.rar.html (29mb)

[tebasuna51]

Yep, you need adjust your player.

The aac file is slightly (1.6 dB) more loud than the ac3 file.
Detailed info by channels:
Statistics: ac3 file mp4 file
-------------- ------------------- -------------------
RMS power ch0: 2.44% (-32.24 dB) 2.96% (-30.58 dB)
RMS power ch1: 2.14% (-33.39 dB) 2.59% (-31.75 dB)
RMS power ch2: 4.18% (-27.57 dB) 5.02% (-25.99 dB)
RMS power ch3: 0.16% (-55.73 dB) 0.28% (-50.98 dB)
RMS power ch4: 0.76% (-42.43 dB) 0.91% (-40.79 dB)
RMS power ch5: 0.76% (-42.41 dB) 0.92% (-40.75 dB)
-------------- ------------------- -------------------
Max value ch0: 41.69% ( -7.60 dB) 46.36% ( -6.68 dB)
Max value ch1: 44.71% ( -6.99 dB) 50.75% ( -5.89 dB)
Max value ch2: 100.0% ( 0.00 dB) 100.0% ( 0.00 dB)
Max value ch3: 18.45% (-14.68 dB) 29.58% (-10.58 dB)
Max value ch4: 14.70% (-16.65 dB) 19.48% (-14.21 dB)
Max value ch5: 14.42% (-16.82 dB) 20.08% (-13.94 dB)

[Sem]

so what do you recommend i do?

[tebasuna51]

so what do you recommend i do?
The problem isn't the conversion ac3 -> aac. You are making good conversions.

Return to first post:
"im using MeGUI to convert a dvd into a mp4 for playback on my ps3"

I'm searching about play video in ps3 and I have some questions:
Ps3, can't play DVD's?
How play you the ps3 audio? With optical/hdmi conexion to a receiver?
The receiver can decode aac audio?

Maybe is better preserve the ac3 audio, all receivers support ac3 decode.

[Sem]

the PS3 can play DVDs but i like to transfer some of my favourite films MP4
so i can play them easily without having to put the disc in as normally a game is in there and i dont like having to constantly change discs

normally i will keep the AC3/DTS if its only got a single track and encode as a AVCHD

but with futurama there are 2 audio tracks so my only option is mp4/aac

the ps3 is connected using HDMI
currently i use headphones (Sennheiser HD555) connected directly to my tv
but i plan to get some 5.1 speakers soon
so even though im hearing 2.0 right now i still want 5.1 encodes for the future

thanks for all the help anyway

[tebasuna51]

...
the ps3 is connected using HDMI
currently i use headphones (Sennheiser HD555) connected directly to my tv
but i plan to get some 5.1 speakers soon
so even though im hearing 2.0 right now i still want 5.1 encodes for the future

thanks for all the help anyway

Ok. Really I don't know how PS3 send the multichannel audio to the TV, but to listen with headphones a downmix is needed. Maybe there are differences when downmix ac3/aac.

Your aac are ok, I can't help you more.

[Sem]

thanks for your help ive learnt alot about AAC encoding

one last thing
what program did you use to compare the AC3/AAC file

[tebasuna51]

I uncompress the ac3/aac, with neutral and tested decoders (like I explain for ac3), to wav. After you can load the wav files in an audio editor (Audacity, Wavosaur are free). The info was generated by Wavosaur.

To decode aac -> wav you can use free tools like BeHappy (Bass libraries), Foobar2000 or Faad.

[Sem]

i know its an old thread..
but i found out why my AACs appear to play with a much lower volume than the original ac3 file

its turns out tebasuna51 was right it was media player classic

all i had to do to restore the correct volume was go into MPCs options and untick AAC from from Internal filters

:)