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Old 11-02-2010, 20:03   #16
drmdab
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Hi Ludo,

thanks for your reply. It's always good to see broadcasters interact with their listeners on forums like this one.

First of all, the audio-quality on your broadcasts is not bad.
But I notice that some transmissions sound very "metallic" (e.g. REE Spain, RRI Romania, BBC & DW sometimes) while others sound a little bit "warmer" (HCJB managed to do this when they were using about 16 kbps, see also BNR Bulgaria). I know that I am going into the direction of the muffled AM medium-wave sound again but I hate it if my ears are hurting because of listening to a DRM station that has very strong high sound-frequencies* and nothing into the direction of bass. I have to admit that this is quite difficult to realize at <30 kbps AAC+...
How do the other users think about this?

* now I am reaching the limits of my English skills.

I would love to see a discussion about the DRM sound-quality here on the forum as we mainly focussed on the transmitter-technology before. Maybe we should use another thread for this?
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Old 11-02-2010, 20:17   #17
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Quote:
Originally Posted by drmdab
Hi Ludo,

First of all, the audio-quality on your broadcasts is not bad.
But I notice that some transmissions sound very "metallic" (e.g. REE Spain, RRI Romania, BBC & DW sometimes) while others sound a little bit "warmer" (HCJB managed to do this when they were using about 16 kbps, see also BNR Bulgaria). I know that I am going into the direction of the muffled AM medium-wave sound again but I hate it if my ears are hurting because of listening to a DRM station that has very strong high sound-frequencies* and nothing into the direction of bass. I have to admit that this is quite difficult to realize at <30 kbps AAC+...
How do the other users think about this?

I would love to see a discussion about the DRM sound-quality here on the forum as we mainly focussed on the transmitter-technology before. Maybe we should use another thread for this?

Would be interestig to have others opinion on audio quality.

Do I understand it right that for you the main difference for a "warm" or "metallic" sound is the absence or presence of higher frequencies? In that case, it could be achieved by turning off the SBR, I think. On the other hand, SBR was developed to restore the higher frequencies which often disappear by compressing to low bitrates, isn't it?

We believed that by using AAC+SBR+PS, we would achieve the closest result compared to the original audio. But we are open to suggestions in order to improve our overall audio quality. It would be nice to have a sound that is as original as possible, warm and not metallic, taking into account the limitations by compressing extensively.
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Old 11-02-2010, 20:40   #18
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Oh I am a difficult listener I think... and I am no skilled sound-engineer.
Sometimes it sounds like the higher frequencies are especially highlighted, perhaps that's the SBR. I will try to compare some AAC+ files / transmissions on the weekend with SBR and without SBR. Maybe I can post a detailled statement then. Often it seems that to many Optimods and sound-"optimizers" deliver worse sound than you'd get if you'd use the original only. But that's a guess.

Very often you can really hear the bubbling digital audio artefacts in the background, even if it's a broadcast with speech only.

As I said I will try to listen to some DRM broadcasts tomorrow and will provide some audio-samples. Maybe we could listen to them and discuss about their quality.
Have a nice evening.
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Old 11-02-2010, 20:46   #19
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I think for the 6015 kHz TDP and The Disco Palace broadcasts the transmission parameters and audio encoder settings (with AAC+SBR+PS) are a good choice and pretty much the best you can get. I donīt think the difference between a warm or metallic sound is just the presence or absence of high frequencies, so please do not turn off SBR, probably this is more a matter of sound processing. Unfortunately we can not compare with the original.
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Old 12-02-2010, 02:42   #20
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Audio from here in the Americas

In listening to TDP from Sackville, I've always found the audio to be excellent. Tomorrow I'll be able to listen to TDP and Disco Palace and I'll report back on how the sound from Montsinery 'sounds.' Based on my past experience in listening to tests from there, it has always been good, so I don't expect tomorrow's broadcast to be anything less.

As to a metallic sound, I've never heard one from TDP. I actually have tinnitus in both ears (the constant ringing sound), so I try to treat them well. I am very quick to identify poor, distorted audio and turn it off, and that has never been my experience with TDP.

Of course, listening to Vatican Radio direct from Santa Maria di Galeria is good for comparison, and lately that service has been quite good despite the slower bitrate and distance involved. For mono, VRI is quite good (14.48kbps), and RNZI also runs excellent audio at 17.08kbps on their Pacific service. If you can catch RNZI's interval signal when they shift frequencies, listen for the bell birds calling in the forest. You will here a clear, close call from a bell bird, and then an extremely faint answer from another bird much farther away. I first heard that on the analog service, and was quite pleased to hear it carry over into the DRM service. Even studio noise can be heard at times during the news or live programming from NZ National Radio. Clarity is important for me.

I'll be back tomorrow, late CET time.
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Old 12-02-2010, 15:12   #21
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Good results again today.
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Old 12-02-2010, 15:40   #22
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Quote:
Originally Posted by simone
I donīt think the difference between a warm or metallic sound is just the presence or absence of high frequencies, so please do not turn off SBR, probably this is more a matter of sound processing. Unfortunately we can not compare with the original.
Simone

We do, on purpose, not use any sound processing. The idea is to have the sound as original as possible.
If you want to compare, that is possible with the live internet stream, which is simultaneous with the DRM broadcast. But this is a 128 kbps mp3 stream, so not really original neither.
The original audio from the studio is lossless audio, so nothing lost in the chain. We only do 1 encoding into DRM and for the internet stream 1 encoding to an MP3 stream.
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Old 12-02-2010, 17:22   #23
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Dear Ludo,
yes, had already been thinking about comparing with the internet stream but as you say thatīs not original either, did not have time yet but will do that comparison, although I would assume you already did that and you were satisfied with the results.
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Old 12-02-2010, 19:24   #24
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Audio quality today

Hello Ludo, Simone,

Much as I thought, the audio here today on TDP and then Disco Palace on 17755 was the usual high quality. Nothing heard that shouldn't be there. If anything, I can tell that the high frequencies aren't as high as they would be on FM (in spite of the 51 year old ears here), but the difference is only very slight really.

I'll have my log in about 3 hours, once my computer is done with all the different broadcasts this afternoon.
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Old 12-02-2010, 21:20   #25
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Hello, hello, hello.... a new label indeed.... Much interesting music, I like it better than the other "steel factory brand"....
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Old 13-02-2010, 17:00   #26
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Good results again today.
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Old 14-02-2010, 12:42   #27
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I am not able to use my DRM receiver today so no report from here today.
Maybe you want to join me in this thread and continue discussing about the audio-quality of DRM. I think we should use this thread for TDP's transmission only, shouldn't we?
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Old 14-02-2010, 14:40   #28
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Good results as usual, I also switched between the internet stream and DRM a few times, there is a rather small difference as the audio bandwidth on the internet stream is a bit wider, see second attachment showing the frequency analysis of both during the same song.
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Old 14-02-2010, 14:50   #29
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... and another example with more detailed sceenshots of the frequency analysis.
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Old 15-02-2010, 14:51   #30
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Good results with a few small dips as usual.
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