Dreamcast Guides : DCRes ADX Downsampling/Looping Tutorial

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Downsampling ADX files

by TuxTheWise


Why would I want to do that?

- Reduce size of your game, so it can fit on a CD-R.

- Reduce total data streaming.


1. Introduction

If  you  followed  "Extracting  data  from  GD  dump  files"  (included  on  this  pack),  you

could extract files of a GD dump with success. Then, you followed "Making GDI files

bootable  on  real  Dreamcast  with  perfection"  (also  included  on  this  pack)  you  are

able to make a perfect CD-R bootable version. But,  when you tried it, you realized

that the game is too big and won't fit on a CD-R. Somehow, you need to reduce the

size of the game. If the game has .ADX files, then you can downsample it and get the

space you need.


ADX  files  are  sound  files.  They're  usually  used  with  music,  because  they  can  have

loop markers, making the sound go back to a determined area when it reaches the

end. In this guide, you'll learn how to downsample these music and reconstruct loop

markers. I've seen some releases on internet where people didn't pay attention on

loop markers, and they were just removed on downsampling process. It made music

stop all of a sudden, what is pretty annoying.


Maybe  you're  wondering  how  much space you can make downsampling ADX files,

and how bad quality will be after the process. About the space, you can save a lot.

That's  because  ADX  files  have  stereo  channels  encoded  separately,  not  joint  as

(most)  MP3  files.  So,  if  you  make  music  mono,  you'll  reduce  size  to  half.  Another

point about space is that ADX files have constant bitrate, not variable. It means that

you  can  determine  space  reduction  easily  with  enough  precision.  Here  is  a  little

table with bitrates of most common ADX encoding:


44khz, stereo: 396 kbits/s

44khz, mono: 198 kbits/s

22khz, stereo: 198 kbits/s

22khz, mono: 99 kbits/s


Most ADX files are encoded in 44khz stereo, so 44khz mono is the best option when

downsampling  then.  You'll  reduce  size  per  half  and  quality  loss  will  be  very  small.

Some people prefer to use 22khz stereo, the effect in size will be the same, so it's up


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to you to choose an appropriated format. I personally think that 44khz mono is the

best option. Any lower quality will make sound quality too bad.


A game you may want to try is Jet Grind Radio. It's too big to fit on a CD-R, but if you

mono the ADX files (downsample to 44khz mono) it will fit easily.


There are cases where monoizing the ADX won't be enough to save the space you

need.  Of  course  you  can  try  lower  quality,  but  as  I  said,  quality  will  be  too  bad.

Instead of doing that, I recommend you try other strategies, like downsampling .SFD

movie files (there is another tutorial included on this pack). Downsampling movies

can  save  much  more  space  than  audio  with  less  quality  loss.  A  typical  case  where

monoizing the sound is not enough to make game fit on a CD-R is Sonic Adventure.


ADX is used mostly on Dreamcast games, but there are games of other consoles that

use them (usually Dreamcast ports). This method probably will work on them too,

but I haven't tested.


To  finish,  be  aware  that  method  explained  here  were  learn  after  months  of

experience.  It  will  provide  the  best  quality  possible  in  downsampling  process,  and

it's the fastest way to do it.


So, it's time to start. Make a folder c:\adx and move all the ADX files you want to

downsample there.


2. Decoding files

First  step  to  downsample  the  files  is  converting  them  to  WAV.  It  seems  to  be  the

simplest  part,  but  it's  not.  There  are  a  lot  of  "adx2wav"  converters,  but  some  of

them  are  very  bad.  Some  converters  messes  the  volume  of  tracks,  mainly  on  not

44khz sounds. Others just output distorced sound. The best decoder I've ever found

was the one bundled on Foobar 2000. It works very good on any .ADX I've tested,

and doesn't mess with the volume, so let's use it.


Open Foobar. If it's not the first time you use it, delete any file that is on the playlist.

Go File, Add Files... and select all the ADX files  of c:\adx, they will be added on the

playlist.  Have  all  the  songs  of  playlist  selected.  Right-click  one  of  them,  Convert,

Convert to Same Folder. On Encoding Preset, have WAV selected. All other options

must be disabled. Click "More Setting". In field Single tracks, replace the text there

for "%title%" (without quotes). It will make foobar2000 use the same name of input

for the converted file, instead of putting a number before it. Click Close. Then click

OK and foobar2000 will convert files to .wav, it will take a while.


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Don't delete the original .ADX files yet, we still need them for loop markers data.


NOTE:  I  heard  that  the  "ADX_Converter.exe"  is  a  good  decoder  too,  but  I  haven't

tested it too much. If you want to try it, don't forget to mark "0" on Fadeout field. I

personally think foobar2000 is better.


3. Downsampling sounds

When  we  encode  the  sound  in  ADX  again,  the  encoder  will  use  source  file  as

information  about  encoding  configurations.  For  example,  if  source  file  is  mono,  it

will encode a mono ADX, if it's 44khz, it will encode in 44 khz, and so on. We'll use

our just converted WAV as source, so any change we want to make in ADX we will

make  in  the  WAV  now.  For  that,  we'll  use  GoldWave. There  are a lot of programs

that  can  make  it,  so  fell  free  to  use  your  favorite.  I  like  GoldWave  because  it  has

Batch Conversion feature that let us encode everything at once.


Open GoldWave. Click File, Batch Processing. Then click Add Files and select all the

WAV   that   you   converted   before  using  foobar2000.  At  the  Convert  tab,  keep

"Convert  files  to  this  format"  marked.  In  "Save  as  type"  select  "Wave  (*.wav)".  In

Attributes,  select  "PCM  signed  16  bit,  mono"  if  you  want  to  mono  the  sound  (if

you're converting to 44 khz, you'll use that option) or "PCM signed 16 bit, stereo" if

you want to keep sound stereo. Your sound is probably 44 khz (check it opening an

ADX on foobar2000). If you want to downsample it to 22 khz (not recommended),

you can mark "Rate (Hz)" and select 22050. If you want to keep 44 khz (unchanged),

just  let  this  box  unmarked.  In  "Process"  tab,  be  su re  no  effect  is  added.  In  Folder

tab,  keep  "Store  all  files  in  their  original  folders"  marked  and  "Overwrite  existing

files"  too,  so  it  will  replace  the  original  sound  for  your  downsampled  ones.  Click

"Begin" and it will convert the files. It may take a while.


4. Encoding the files

Darkfalz has made a very useful tool for batch encoding ADX files with loop, let's use

it. Open ADXLoopCalculator.exe (included somewhere  else in this pack). Select the

directory c:\adx. You can keep "Delete ADX" marked, so it will automatically delete

ADX after using them to determine loop markers. Click Calculate. The program will

scan  for  loop  markers  in  ADX  files,  and  create  a  BAT  file  containing  the  correct

command line for encoding ADX with them. Don't worry, if the ADX file has no loop

markers, the correct command line will be used. After program is done, a file called

"encode.bat"  will  be  created  on  c:\adx.  Before  executing  it,  move/copy  the  file

"adxencd.exe" to c:\adx. Now execute encode.bat and it will start encoding the files,

it may take a while. After done, your job is ready. The re-encoded ADX will be in c:


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\adx, they will be smaller than original ones and you can use them instead in your

game.


5. Final comments

Downsampled ADX files worked fine with me most of the times, except two times.

One  was  in  Jet  Grind  Radio,  when  I  tried  to  monoized  some  songs  and  let  others

stereo.  Original  music  worked  fine  of  course,  and  when  I  monoized  all  the  ADX  it

worked fine too. But if I kept some stereo and some mono, in transition of the songs

(for example, when it was playing a stereo song and started a mono) game crashed.

Other  problem  I  had  was  in  Fatal  Fury.  Song  was  stereo,  but  after  I  monoized  it,

music played only on right channel. Well, if something like that happened to you (I

doubt it will happen, but anyway...), look for alternatives. In my case, for example, I

kept all songs mono in Jet Grind Radio and used 22 khz stereo in Fatal Fury.


6. Thanks

- The nice guys who created the programs used here.

- Darkfalz for the random information let in forums in the past.

- This wonderful site tutorials

 http://www.dreamwell.pwp.blueyonder.co.uk/dcselfboot/index.htm) for my first

contact with downsampling process.

- All people that rip and distribute GDI.


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