Thursday, October 20, 2011

Voice of Russia DRM transmitting with two audio streams

(UPDATED 20111022 with image from Alokesh at bottom of post)

Glenn Hauser's DX Listening Digest (also Glenn's World of Radio) featured a report from Giampiero Bernardini in Milan, Italy. He mentioned hearing Voice of Russia on 9850 kHz at 0820z on the 7th of October broadcasting in DRM with 2 audio streams. I have always thought that this is a great and innovative use of DRM. I certainly wish I had more information, but it was described as in English and Russian "DRM RUVR 1A" & "DRM RUVR 1B"

If my knowledge of DRM is correct, this could be done in CELP or HVXC using two 8 kHz or similar audio streams. This would be near the robusteness of what we are used to with RNZI broadcasting one stream of 15.48 kHz AAC+.

Here is an example of a short SPEEX audio clip at 8 kHz (based on CELP). Frankly, I'm quite impressed at the quality. In a 9 or 10 kHz wide channel, 2 audio channels of this quality could be supported in a fairly robust DRM broadcast framework. In an 18 or 20 kHz channel, 4 such audio channels could be supported (or 2 channels of nearly 17 kHz quality - like RNZI's current audio).

It seems to your admin, that this is an excellent way to serve multiple linguistic audiences that share the same location. It also stands to reason that one broadcast that covers two languages potentially cuts broadcast on-air time in half. At the reduced power requirements already present with DRM broadcasting, even more cost is reduced.

Couldn't Canada use this to serve their English and French speaking audiences throughout the country? What about parts of the USA where Spanish and English are both spoken? You get the picture.

Have you heard a DRM broadcast employing multiple audio feeds? Report about it on our drmna Yahoo group. Maybe improved HF conditions will allow us to copy one of these unique broadcasts soon.

(UPDATE) Here is a partial DReaM grab (Thanks Alokesh!) of the 2 channels. They are not even using the same audio compression scheme on each one and the total is 20.96 kbps (the same bitrate employed by Disco Palace from Montsinery).

(20111027 UPDATE)
In addition Mario from the drmna Yahoo group posted this IF recording of the dual language broadcast. Thanks Mario!