Bit rate question about MPCM on Rotel 1069

[kmcheng]

I was playing the newly released Chris Botti in Boston blu-ray disc last night, and it looks and sounds fantastic. The musicianship of all the artists are superb.

Anyway, I use the PS3 to play blu-ray, and this disc has a 96k Dolby TrueHD sound track. However, the 1069 front panel display shows that it is playing a 48k MPCM sound track. I get the PCM part because I know the PS3 is doing the decoding, but shouldn't the 1069 show 96k instead of 48k? Am I missing somthing here? Are all MPCM tracks 48k after decoding from Dolby TrueHD and DTS HD MA tracks?

[Hammie]

Do you have any LPCM above 48Hz selected in the Audio Output settings? If not, then it will downgrade the audio to 48Hz.

Just a thought.

[WI Rotel]

I'd like to know too! My guess is that the player is reading the 48 rather than the 96K track, the 1069 will play 96K. On the other hand the BD players will only do 96K on a limited number of channels, if their decoding ability is exceeded they will use a lower sampling rate. My guess is that the PS3 cannot handle 5.1 at 96k sampling rate.

[kmcheng]

I'd like to know too! My guess is that the player is reading the 48 rather than the 96K track, the 1069 will play 96K. On the other hand the BD players will only do 96K on a limited number of channels, if their decoding ability is exceeded they will use a lower sampling rate. My guess is that the PS3 cannot handle 5.1 at 96k sampling rate.

If it is true, that would be a shame for the PS3.

On louhamilton's suggestion, I checked the audio output setting and saw that I selected "automatic" which includes everything up to 7.1 channel PCM @ 192k. As an experiment I also tried "manual" and checked the box for 7.1 channel PCM @96k. In both cases, the front panel of the 1069 showed only multichannel 48K.

I am suspecting one of my HDMI cables might be 1.0. Does anyone know if HDMI 1.0 can handle 7.1 channel 96K PCM? My TV is showing a 1080p picture, so the video portion is fine.

By the way, I just realized that this thread should really be in the Rotel forum. It would be great if an administrator can help me move the thread. Thank you very much!

[kmcheng]

Okay, so I did some more research and found out that HDMI 1.0 will not be the cause of the said problem.

Now I think it must be an issue specific to the disc title. I tried a different bluray disc (a concert by a Hong Kong pop singer called Hacken Lee), which has a DTS HD MA 5.1 96K 24 bit sound track. Voila! The 1069 shows that it is now playing 96K MPCM.

And then I tried a third bluray disc (another Hong Kong pop singer Andy Lau) which also has a DTS HD MA 5.1 96K 24 bit sound track. This time, the 1069 shows 48K MPCM again.

These observations lead me to conclude that the codec decoding must be title-specific. Some titles are 96K when decoded to PCM, whilst others are decoded to 48K PCM.

Alright, I think that's enough geeky number crunching already. I should just go back to enjoying the concert DVD. Whether it is 48K, 96K, 4K, or 8K, this new Chris Botti release is really something extra ordinary. Highly recommended!

[kmcheng]

Now I feel really stupid.

I revisited louhamilton's post, and played with the PS3 some more, and suddenly I realized that after I changed the audio output setting to "manual", I also NEED TO SAVE it! :E

Now the 1069 is showing 96K.

My previous default for 7.1 PCM was 48K all along, and I never realized that. In my defence, this Chris Botti blu-ray is probably the first 7.1 sound track that I have ever played with my PS3, so I never came across this issue before. Still, stupid me.

So is there a difference between 96K and 48K? Yes, but I think it is rather subtle. However, either resolution will be a big improvement over the PBS broadcast, which itself was my favorite TV show.

[ray5]

For the ignorant here can someone elaborate what is PCM and bit rate?
Ray

[Hammie]

For the ignorant here can someone elaborate what is PCM and bit rate?
Ray

PCM stands for Pulse Code Modulation. Basically it is the digital version of an analog sound wave. Bit rate is the frequency that it is sampled. The higher the number (48, 96, 192, 320), the more samples are captured, and the resulting output will be more accurate.

The best example I can think of visually is a digital camera. The higher the megapixels, the better resolution the picture will be, especially when cropped and/or zoomed.

Hope this helps.