MP3 to AC3 - Bad Sound Quality

[urdivine]

I'm creating a music DVD of which I want to use AC3 at 48khz for the audio.

Starting with MP3s at 48khz and converrting to AC3 at 48 khz, I noticed that they, [after 30 seconds or so], skipped every 2 seconds throughout the whole AC3.

I thought it was just the software [ImToo Video Enc], and when I tried another software, I had the same problem.

Then I thought maybe the software can't encode very well going from MP3 to AC3. So I converted an MP3 to WAV [the WAV sounded good] then converted the WAV to AC3 - 48 khz. Again. Same problem

I then tried converting my original MP3s at 48 khz....to AC3 at 44khz. It sounded fine.

Unless I can solve my problem, I have to resort to either;

1] using AC3 at 44khz [which some DVD players may have a problem with]

2] Using MP2s [which is a lesser quality sound]

Thoughts anyone?

Thank you

[Soopafresh]

I've seen that problem before with 44.1 , and I'm not certain what the answer is. The other issue you'll have to contend with is whether the resampling from 44.1 to 48.0 will change the length of your audio, resulting A/V sync errors. Theoretically it shouldn't, but I've seen that happen as well. Aren't I am optimist ?

I've got a pretty decent script which will convert your audio into 5.1 AC3 . I'll walk you through the process if you're interested.

1) Install Avisynth 2.57
2) Download the script and unzip
http://www.wikiupload.com/download_page.php?id=145103
3)



4)

[FulciLives]

Use a program like Goldwave or Audacity to convert the MP3 to a 16-bit 48k Stereo (2 channel) PCM WAV audio file. Also make sure you normalize the audio file. Depending on who you talk to (and what the source is like) you want to normalize to either 0.0db or -3.0db with -3.0db being the better choice in most instances (knock on wood).

If that (the converted PCM WAV file) sounds good then there is no reason you should have issues converting it to AC-3 unless you are doing something wrong or using a very low bitrate. For 2.0 AC-3 (2.0 meaning 2 channel) you should use a bitrate of 192kbps and no lower. I prefer to use 256kbps myself. Some people like to go 320kbps for "best" quality.

ffmpeggui and Aften are two freeware programs that can do the AC-3 encoding from the PCM WAV file.

- John "FulciLives" Coleman

[redwudz]

What other software did you try? I use VirtualDub Mod, and save out the audio as a WAV with full processing. Then I use ffmpeggui to convert the WAV to AC3. The quality is just as good as the MP3. I think AC3 would be more often encoded at 48Khz sampling rate and 256Khz data rate, no matter which conversion program you use.

[FulciLives]

I forgot to add the following:

Make sure you install the following on your Windows PC:

1.) AC3 ACM Decompressor
2.) AC3 Filter

After you install I would reboot to be "safe" that the install "took".

Also sometimes you have to "play" with the AC3 Filter settings to get proper volume (people often complain the default is set "too low"). After you install AC3 Filter you can find the controls for it in the Windows CONTROL PANEL region.

- John "FulciLives" Coleman

[Alex_ander]

As said, first decompress mp3 to wav, then resample to 48kHz, then encode to ac3.
With music material it is important which tools and methods you use, because of rounding errors accumulating at numerous digital calculations. To minimize those errors, use temporal bit-depth upconversion to 32 bit (Audition, CoolEdit) or 64 bit (SoundForge) at least for resampling:
mp3(44.1/16)=>wav(44.1/16)=>wav(44.1/32)=>wav(48/32)=>wav(48/16)=>ac3(48/16)

For decoding mp3 it's better to use MAD (MPEG Audio Decoder) internally working at 32 bit. It is inside WinLame (free).

[urdivine]

Whoa! Fast replys! Now I have more options. great.

soopafeash....I'm glad you mentioned that potential A/V sync error problem. I'll remeber that for [near] future reference. This, though, is an audio only DVD.

I'm going to start with Avisynth 2.57.

The MP3s are all normalized and are encoded at a bitrate of 192kbps. That was the highest I could go to get all 220 long AC3s on one DVD.

I may not be able to do this, but I do want to encode directly from the MP3 to the AC3.

I do think I do need to install AC3 ACM Decompressor and AC3 Filter.

I know all 3 of you guys are going to lose a lot of sleep until I solve my probelm so I'll try to post when I have success.

thanks again

[Soopafresh]

No worries, urdivine Whatever works for you is the best way to do it.

Hey John, try the script and tell me what you think. Just make sure the MP3 doesn't have spaces in the name. Run the AC3_to_6_mono_WAVS batch file afterwards to check out the tricks it performs.

[urdivine]

I still have the same problem, but I have narrowed down the possible reasons.

It now appears that ANY file I use to convert to AC3 at 48khz, the results are the same.

I tried different MP3s at 48khz and MP3s at 44khz and WAV files. All sounded great until the conversion to AC3.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I installed Avisynth 2.57 and ran the ms-dos file [mp3_to_ac3] and it went thru the process but there was an error message at the end that flashed too quickly for me to read.

I installed - ffmpeggui which produced the same problem

I installed AC3 Filter and I can open [ ac3config ] in Explore - Program Files, but all I know to do is keep the default setting as they are.

I installed the AC3 ACM Decompressor.

I installed winLAME and it does not look like it will encode to AC3.

Besides the above, I have the following software that may be appropriate:

Adobe Audition 2.0 ------- GoldWave -- VirtualDub 1.5 ---- VirtualDubMod -------- DAudioK --- TMPGEnc --- Audacity -- BeSweetGUI [which I can't even figure out yet] --Blaze Media Pro -- ImToo Audio enc

Thanks again

[Soopafresh]

Post an Mp3 and the resulting AC3 up here. Make sure file sizes don't exceed 2 MB each.

Does this sound OK on your system ?

input.ac3

Regarding that "flashing" in the batch file, make sure your input Mp3 file doesn't have spaces in the name.

[urdivine]

Soopafresh;

Yours sounded good because it was too short. All of my encoded AC3s have sounded good for about 40 seconds ["i put 30 seconds or so" in my first post].

I'll try to upload the MP3 & AC3. tHey are less than 2 mb each.

[Soopafresh]

Spaces in your file names are causing you woes...

kitaro-destiny.ac3

[urdivine]

Well, I thought that idea was too good to be true, but I was sure hopeing. I just converted kitaro-destiny [no spaces] and had the exact same results. I wish it was something that superficial, but it may be a deeper problem.

[Soopafresh]

How does the file above sound ?

With my batch, another requirement is .NET 1.1 or higher.

[urdivine]

I just tried that same MP3 [no spaces] conversion with your...mp3_to_ac3 you gave me. It did go thru the whole process as it never did before. But same results.

[Soopafresh]

Listen to the AC3 of Kitaro. Does it sound OK ?

https://forum.videohelp.com/images/guides/p1703629/kitaro-destiny.ac3

[urdivine]

It sounds the same. Terrible.

I don't understand [ With my batch, another requirement is .NET 1.1 or higher.]

[Soopafresh]

Nevermind. It is your playback mechanism on your PC, as the AC3 sounds perfect on my system. Something is up with 48Khz sampling rate. I've got a different player for you to try, gimme a minute.

Edit - Try this self-contained player. Open the AC3 with it.

http://ffdshow.faireal.net/mirror/mplayer/gmplayer2007.04.02.7z

[urdivine]

I think you have it. I didn't dream it was a problem with the players.

I tried

Nero Showtime -same results

Windows media classic - sounds good

If you have good player and if you don't mind, I'd prefer that over Wndows Media Classic

[Soopafresh]

VLC should work, but it isn't very loud with AC3.

[urdivine]

I have an old version of that that I deleted some time ago. I'll install that version and give it a try.

Anyway. Mission Accomplished. Thank you again.

[FulciLives]

Hey John, try the script and tell me what you think. Just make sure the MP3 doesn't have spaces in the name. Run the AC3_to_6_mono_WAVS batch file afterwards to check out the tricks it performs.

I tried the script.

My source was a CD audio track ripped to MP3 format using 320kbps and since it came from an audio CD the sampling rate was 44.1k with the only change being that I normalized to -3.0db before converting to MP3 format.

Used your script and it made a 5.1 AC-3 audio file at 48k and it sounds good to me.

I put the original MP3 and AC-3 into a RAR file using no compression. This way you only have to download one file (which is why I did that).

Here is the link ---> http://rapidshare.com/files/31749324/ProfondoRosso.rar

My only complaint? The MP3 was normalized to -3.0db (which actually raised the volume from the CD rip) but your script seems to use 0.0db (I am guessing) because it made it sound "too loud" on my tiny computer speakers LOL

- John "FulciLives" Coleman

P.S.
Below is a graphic of the MP3 in GOLDWAVE followed by a graphic of the 5.1 AC-3 in Soft Encode [please note the images are 1280x1024 which is my desktop resolution]

[Soopafresh]

Hey, thanks a lot, John. I appreciate the time you spent. Yeah, the volume thing has been a source of contention - make it the same db and folks complain that it isn't loud enough, or make it louder and risk bouts of nasty digital distortion. Good point on processing music mp3s - no need to kill the dynamic range by cranking up the track volume. I'll make some modifications for the next revision. thx