Does iDVD support 24 bit audio?

Question

I have a project that calls for impeccable audio quality. The client has supplied me with 24 bit aiff files.
The files import easily into Final Cut Express and when placed in the a 1080i60 timeline show no sign of needing a render.
Does this mean that I will retain the 24 bit quality all the way through export to authoring of the DVD in iDVD? Does iDVD compress the audio in such a way that it will no longer be 24 bit?
I can find little or no information about this particular question in the manuals or the discussions.
Thanks in advance.
Mike Pulcinella

Answer 1

Apple has never said much about the audio encoding in iDVD.
'Traditionally' it was just two channel uncompressed PCM audio; DVD SP (with Compressor) gives several other choices (including Dolby Digital).
Toast gives you the choice of uncompressed PCM or Dolby Digital as well.
Here is what the Toast manual has to say: Audio Format: Choose Dolby Digital or uncompressed PCM. In almost all cases, Dolby Digital is the best choice. It uses less disc space, so you can fit more video on the DVD, and the sound quality is almost the same as PCM.
Data Rate: Choose the bit rate to encode the Dolby Digital audio. Higher bit rates can produce slightly better sounding audio, but use more disc space. Toast uses 192 kbps by default.
Dynamic Range Compression: Enabling dynamic range compression reduces the range between loud and soft sounds in order to make dialogue more audible, especially when listening at low volume levels.
PCM audio should be used if you want to maintain 100% fidelity and only if the audio source is already uncompressed PCM, such as tracks on an audio CD or a high quality audio recording. If the audio files are already compressed (such as MP3 or AAC songs in your iTunes library) do not use PCM—it will not improve the sound quality.
Toast records PCM at 48 kHz / 16 bit levels or 48 KHz / 24 bit levels, which are higher than standard CD quality. Audio that has been recorded at 96 kHz / 24 bit is downsampled automatically unless you choose the 96 kHz / 24 bit option, which maintains the higher quality but significantly reduces disc space.
When you choose PCM, any existing Dolby Digital audio files will be “passed through” without reconverting to PCM.
Hope this helps.