OPPO BDP-83 and 24bit lowest-byte data

June 29, 2010

The spectral scans presented here show clearly resolved sine wave data in the LOWEST byte of 24 bit LPCM multichannel data, from the surround multichannel analog outputs of the OPPO BDP-83 Blue-ray player.
A DVD-A disc was authored with dvda-author 9.05 with the following simple design:

There are 6 Groups with one track per group. All tracks are 5.1 LPCM 24bit/48kHz audio content with: This very low audio level corresponds to -96dBFS relative to the full signal amplitude of 24bit signed integer audio data.
The output of the 3 pairs of analog multichannel 5.1 outputs was analyzed in frequency using RMAA 6.2.1 while playing back each of the 6 DVD-A tracks consecutively. Each audio output pair was in turn connected to the Line-in connection of a Creative X-Fi Elite Pro sound card and the audio was analyzed with RMAA.
As expected the 2 kHz low level audio data is ONLY seen from the channel output corresponding to the input channel of the Group containing data for that output channel. For each pair of tested output channels, FL/FR, C/LFE, SL/SR, all 6 audio tracks were played back and viewed to verify this.

The first image shows the background spectral content of any 2 output channel pairs during playback with track content in the other input channel pair.

The next six images show the spectral scans consecutively for the audio data in FL, FR, C, Sub, SL, SR.

This data clearly shows that the original 5.1 multichannel wave file data is correctly packed into the DVD-A AOB structure and further that the BDP-83 properly decodes the 24 bit 6 channel interleaved data from the AOB structure. It is of course possible to use large amplitude signals to check for proper channel input/output mapping, but it is also important to verify the proper mapping (and no mixing) of sample data at the lowest bit level, which is measurement has focused on.
Creating simple DVD-A test discs with this type of content can be extremely useful in understanding and exposing problems with multichannel implementation artifacts.