Dolby Digital 5.1 Surround on a CDR

Click Here To Start How To Burn Dolby Digital to a CDR

If you've ever wanted to put your own music in 5.1 surround onto a CD-R you can do so. It does work! I've done it many times now without any problem.

We will be adding a Surround Test 5.1 file soon. This file will be used for testing your consumer playback system (for Dolby/DTS Playback Receivers). There will also be a file that can be used for calibrating your 5.1 surround mixing system (for sound engineers).

Dolby Digital 5.1 Surround n a CDR

First I'd like to say that for the most part Dolby Digital is the same thing as AC-3. It is an audio data compression scheme that allows you to multi-plex 6 channels of audio information into a single digital stream. This digital stream is then sent to your Dolby Digital (AC-3) decoder where it is decoded back into PCM audio and then output to your speakers. The main reason for AC3 is that it makes the file size much smaller than that of PCM. There is about a 11:1 file size reduction. Clearly this is a major advantage over PCM especially with DVD-Video. I'd like to also mention that DTS 5.1 encoding is made for CD. You can use a DTS encoder to encode your 5.1 mixes and put them onto a CD-r. There is quite a market for these 5.1 surround mixes.

AC-3and DTS can be put onto a CD-R and played back on any CD/DVD Player with a digital (S/PDIF or Toslink) digital output which is connected to a DTS/AC-3 receiver (decoder+amplifier). DTS has a superior sound than that of Dolby Digital (AC-3) mainly because of the higher bit rate used by DTS.  For playing back music in 5.1 surround DTS should be used. Dolby Digital (AC-3) is used primarely on DVDs because of the lower data rates (and quality).

The Past:
There use to be a problem with either the CD/DVD Player couldn't read a CDR or the Dolby Digital receiver couldn't decode the audio because it couldn't understand a parameter in the dolby digital stream was compressed audio (AC3) or PCM and would either mute or play short bursts of white noise. Also some DVD Players will not play a CD-R but will play a CD-RW (go figure).

People have told me that there system can't playback AC3 files at 256 kbps. I haven't run across this but at some point in the future I may update the files to 384 kbps rate.

Before purchasing a CD or DVD player check out: DVDRHELP.COM and see what the formats it's capable of playing.

Above is what a Dolby Digital Wave File looks like. This is a very small segment which has about 140msecs of 5.1 dolby digital information. This isn't PCM audio data and can not be treated as if it where. This means you can't do fades (or Crossfades) you can apply dither or EQ etc... The information shown above represents audio that has been compressed and needs to be decompressed (decoded) before you can actually hear it. If you download one of the above Dolby Digital Wav files you will see that the file has been made smaller to save on download bandwidth using WinZip. Again looking at the above Dolby Digital file view you will notice that there is more space (zeroes) than there is data so the wave file size will be about 6 times larger when you put it on your hard drive.

This on the other hand is a graphical representation of what a DTS wave file looks like. Again this is compressed audio and needs a DTS decoder to hear what it actually sounds like.

Here is what a normal PCM audio file looks like. You can see that there is a big difference in the sound. This has amplitude and modulations etc... things that normal analog sound has. Again this is a 2D graphical representation of what PCM audio looks like.

The sound quality of AC-3 seems to be better than that of MPEG but you can decide for yourself. The really great thing about this is the fact that you can deliver 5.1 audio over the internet, with the same sound quality as MP3, using twice the bitrate. What that means is if you set the bitrate for your encoder to 256kbps you end up with a file size that is about twice that of a 128kbps MP3 file. Now we just need to be able to stream AC-3 right off the server.

How to Create a Dolby Digital Audio CDR

Step 1: Do a 5.1-surround mix. Record it discretely on 6-track as 6 separate WAV files in your computer.

Step 2: If the discrete audio tracks are on an ADAT or D98 etc.... You'll need to get them into your computer as separate wave files into your computer. I've done it using 16/44.1 files, and it should work at bit lengths and rates at up to 24-bit / 48 kHz but you will need to use the 44.1k Sample rate if you want to put it on a CDR.

Step 3: Open the files in a Dolby Digital Encoder and assign them to the proper channel (L, C, R, Ls, Rs, and LFE).

Step 4: You will need to change some of the default parameters in order to encode at 256kbps and 44.1k samplerate. If you leave the audio at 48k and switch the encoder settings to 44.1k your music will playback faster that it should. You will need to set the encode parameter to 3/2 Mode. You can enable the LFE channel if have one otherwise leave it off. Next select the Data Rate to 256 kbps and the Sample Rate to 44.1 kHz. If you decide to use a higher datarate then the resulting file size will become larger and the sound quality will be better :^) Some people have said that there DD receivers can't decode using the 256kbps setting so do some test pressing to see what your receiver can handle. Hint: use a CD-RW

Step 5: Go to the File, Save-As pull-down and set it to save as a Dolby Digital WAV (*. WAV). Some encoders have a "record" button but some are "Save As" either way what you'll end up with is a Dolby Digital Wav file. You cannot put use the *.AC3 extention as it's not in the redbook spec. The wav file extention bascially pads the file with zeros (see the above picture) and the AC3 extention does not. If you know of a program that will convert the *.ac3 files to *.wav files please let us know.

Step 6: How To Burn an Dolby Digital Audio CDR

The process for creating your own AC-3 CD-r is simple. If you've ever burned an audio cdr then you should be able to use the above Dolby Digital wave files and create your own 5.1 CDR. Each CDr can hold up to 74 or 80 minutes of audio. Again not all CD and DVD Players will be able to read a CDR so check out DVDRHELP.com and see what your player is capable of doing. If you have an older Dolby Digital receiver it may not understand what type of audio is coming off of the CDR and it will either mute or playback small bursts of white noise.

Step 7: Download at least one of the Dolby Digital AC-3 256 kbps Files and un-zip it. It will be about 11 times larger when you unzip the file.

Step 8 : Take the resulting dolbydigital.wav file(s) and open your CD burner application. Hopefully you've made your own redbook audio CD but if you haven't then you should read the manual that came with your burner.

As far as burning the DD wave files to a CDR you can treat them as you would any other Stereo 44.1k 16-bit wave file. You can not however modify the wave file. That means no fading, normalizin, EQ'ing, or applying dither. Nothing. You must remember that the digital numbers in the files are compressed audio data and not PCM data which is what all audio editors use. Some people have told me that they can't seem to get anything to playback etc... I come to find out that they had turned on Dither. Also do not change the volume using a master volume control. The only thing to remember is to not alter anything on the file. You are dealing with compressed audio data not regular PCM audio.

Write the words "Dolby Digital" (TM) one the CDR because you don't want someone putting this in their player and turning it up and blowing out there speakers or experience an unpleasent load noise.

As mentioned before the CDR should be playable on most Home Theater systems. It will not however work on a Dolby Pro Logic System.Pro Logic is a different thing completely. If your receiver doesn't say "Dolby Digital" on the outside then it probably doesn't have a Dolby Digital decoder.

Step 9: Go to the CD-Audio recorder app and load the DD wav files (stereo 44.1k 16-bit) into it and burn the CD using the Audio setting (redbook Audio). I've used Roxio Easy CD Creator with no problems at all. Make sure you mark this as a DOLBY DIGITAL CD disc that's not for playback in an Audio-CD player, as the digital noise will be at full volume level and speaker damage could result.

Step 10: Take the CDR-AC3 disc and play it back in any CD/DVD player that's connected to a 5.1 Dolby Digital Receiver. Turn the volume all the way down! Hit the Play button and then gradually turn it up volume. This is just incase your player/receiver thinks it's a PCM file and plays short burts of white noise.

There are still CD/DVD Player and Dolby Digital Receivers that won't see the CDR as compressed audio data but rather as PCM. If this is the case then you'll hear short bursts of white noise rather than music/sound. If you hear white noise then check your receiver connection, also what input is it using? It should be using a digital input (optical or coaxial RCA). If you are using the analog CD input then there's your problem.

You should know that AC-3 audio found on DVD-Video titles are at the 48k sample rate and not 44.1k that is required for redbook audio CDs. There isn't a way to convert 48k AC3 to 44.1k AC3 without decoding the 48k audio to PCM and then converting each channel, 6 of them, to 44.1k and then re-encoding them.

There are so many ways one can spend their time :^)

Redbook Audio Specifications

The maximum playing time is 78 minutes (including pauses)
There is a minimum time length for a track is 4 seconds
You can not have more than 99 tracks on a CD
You can have no more than 99 index points (subdivisions of a track)
International Standard Recording Codes (ISRC) should be recorded on CD-Rs to appear on the replicated discs