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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#41
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Mono Stereo
In article ,
mm0fmf wrote: The issue with DAB is it is an old crappy codec that doesn't compress the audio as well as modern codecs do. In order to maximise profit, signals are encoded at very low bit rates and strangled bandwidth to squeeze more in. That is how some broadcasters choose to do it to save money. Same happens on FreeView TV. Not an inherent fault with DAB. You might as well say a CD played on the average radio FM station sounds nothing like it does at home. Due to the signal processing all broadcasters use. That is nothing to do with the FM medium. -- *When did my wild oats turn to prunes and all bran? Dave Plowman London SW To e-mail, change noise into sound. |
#42
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On 22/04/2019 11:46, Dave Plowman (News) wrote:
In article , mm0fmf wrote: The issue with DAB is it is an old crappy codec that doesn't compress the audio as well as modern codecs do. In order to maximise profit, signals are encoded at very low bit rates and strangled bandwidth to squeeze more in. That is how some broadcasters choose to do it to save money. Same happens on FreeView TV. Not an inherent fault with DAB. You might as well say a CD played on the average radio FM station sounds nothing like it does at home. Due to the signal processing all broadcasters use. That is nothing to do with the FM medium. The difference in sound between CD and vinyl has nothing to do with the media too. Its down to the different processing needed to get a reasonable sound out of vinyl that they don't have to do on CDs. CDs being closer to the original but some still prefer the distortion in vinyl. |
#43
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Mono Stereo
In article ,
dennis@home wrote: On 22/04/2019 11:46, Dave Plowman (News) wrote: In article , mm0fmf wrote: The issue with DAB is it is an old crappy codec that doesn't compress the audio as well as modern codecs do. In order to maximise profit, signals are encoded at very low bit rates and strangled bandwidth to squeeze more in. That is how some broadcasters choose to do it to save money. Same happens on FreeView TV. Not an inherent fault with DAB. You might as well say a CD played on the average radio FM station sounds nothing like it does at home. Due to the signal processing all broadcasters use. That is nothing to do with the FM medium. The difference in sound between CD and vinyl has nothing to do with the media too. Its down to the different processing needed to get a reasonable sound out of vinyl that they don't have to do on CDs. CDs being closer to the original but some still prefer the distortion in vinyl. It's not distortion - it's "musicality" -- from KT24 in Surrey, England "I'd rather die of exhaustion than die of boredom" Thomas Carlyle |
#44
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Mono Stereo
On 22/04/2019 09:18, mm0fmf wrote:
On 17/04/2019 14:53, John Rumm wrote: On 17/04/2019 13:44, The Natural Philosopher wrote: On 17/04/2019 13:33, John Rumm wrote: On 16/04/2019 23:24, wrote: Does it give a better S/N ratio? IIUC, for reasons of backward compatibility, a stereo FM transmission encodes stereo image into a pair of sum and difference signals[1]. So mono receivers can simply process the sum signal and get both channels combined into a single mono channel. A stereo receiver will need to add/subtract the difference signal from the main combined channel to get the separate L & R channels. The sum signal is transmitted using FM and the difference signal is amplitude modulated onto a sub carrier shifted up from the main carrier. (IIRC there is also a pilot tone included just above the baseband audio to signal the received that its a stereo transmission). Since the AM modulation will suffer more in poor reception conditions it can also introduce hiss. Many radios hence include a Stereo/Mono switch to elect for mono with no hiss. Some of the posher car radios actually use a mixer for the stereo decoding, so they can switch the stereo in and out in gradual way depending on how much noise is being detected. [1] Conceptually not unlike the way colour was added to mono TV Not quite correct. https://en.wikipedia.org/wiki/FM_broadcasting#Stereo_FM is definitive. ..and actually appears to be a fairly close match to my overview above. the reason for worsening S/N is quite simply that more bandwidth is needed to get stereo and that simply lets in more noise. Â*From your source... "The (L+R) Main channel signal is transmitted as baseband audio limited to the range of 30 Hz to 15 kHz. The (Lˆ’R) signal is amplitude modulated onto a 38 kHz double-sideband suppressed-carrier (DSB-SC) signal occupying the baseband range of 23 to 53 kHz." later: "for a given RF level at the receiver, the signal-to-noise ratio and multipath distortion for the stereo signal will be worse than for the mono receiver." AM or FM doesn't really make much odds here. Its the AM modulated difference signal (i.e. the bit that carries the stereo information) that suffers the poorer SNR. Whether one argues that is because or its modulation technique or its the lower bandwidth is a bit moot (I would say both are a factor, but AM is still the better choice for narrowband applications). However I will concede a better wording may have been "Since its the AM modulated part of the signal that will suffer more in poor reception conditions..." What you fail to understand, and it is quite complex, is that the AM modulated part is transmitted over the air as FM. FFS people, I made a comment that the stereo difference signal is more fragile than the main sum of the channels signal. This appears to be something that everyone agrees with, so why keep romping off down rabbit holes about how you name that bit of the signal? Take the L and R signals filter to 15kHz and add them to give L+R and subtract them to give L-R. Generate a 19kHz tone. Double it to 38KHz. Use the 38kHz signal as the "carrier" in a double sideband suppressed carrier AM signal. (DSBSC) Add L+R + 19kHz + DBSSC to give the baseband signal and apply that to wideband FM modulator. The whole lot is transmitted as FM. In reception you receive the signal and demodulate the FM to get back the baseband. You use (normally) a PLL to lock to the 19kHz tone and double it to get a phase locked 38kHZ signal which is used to reinsert the suppressed 38kHZ carrier. You can then demodulate the difference and get L-R. Low pass filtering gives you the L+R signal. Add L+R + L-R to 2L Subtract L+R - L-R to get -2R and invert to get 2R. Yup nice description... Pretty similar to how they described it in our transmissions system lectures some 30 odd years ago. Job done. The stereo FM signal is massively wider in bandwidth than the equivalent mono meaning the signal to noise ratio is much worse. So IIRC you need about 23dB better signal strength for the same signal to noise ratio for stereo over mono. Due to the way FM works, a weak signal will be inherently nosier at higher frequencies which appears as hiss. FM audio is already pre-emphasised to minimise this, the gain rises with increasing frequency into the FM modulator. The interesting issue is human brains can accept and mask out a lot of the imperfections with analogue signals, we just learn to ignore the pops and hiss and hear the music still. Digital signals will sound "perfect" at signal levels that would be noisy for analogue. Then they drop off a cliff and you get burbles and break up and cant hear anything. For certain values of "perfect" - if you make the "wrong" trade-offs in filtering, dithering, sample rate / depth, codec, reconstitution etc its not difficult to end up with something perfect that is not at all pleasant to listen to. The issue with DAB is it is an old crappy codec that doesn't compress the audio as well as modern codecs do. In order to maximise profit, signals are encoded at very low bit rates and strangled bandwidth to squeeze more in. So you get the worst of both worlds perfectly reproduced crap audio and no way to in-situ upgrade to better codecs. Indeed, case in point. In some respects the system development was a little ahead of its time - results would probably been better with another few years of development and experience in digital audio coding, before nailing it down as a standard. (and a more flexible spec would probably have helped greatly). Still if you think DAB sounds bad, try listening to LPC-10 audio encoded at 600 bps. (actually quite intelligible for speech so long as one speaks slowly with distinct gaps between the words) It is completely bogus. But hey never mind the quality... look at the choice of stations.Â* Just that they all sound ****e. With the possible caveat that in moving receiver applications, and high ambient noise environments, you *might* value the lack of fading etc as a benefit that outweighs the loss of absolute quality. Cople that with the fact that many people seem to be blissfully unaware of the lack of fidelity in their audio, and enough people put up with it without that much complaint. (personally if the radio quality is crap I would rather listen to a CD etc anyway). -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#45
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Mono Stereo
On 22/04/2019 11:27, The Natural Philosopher wrote:
On 22/04/2019 09:18, mm0fmf wrote: The issue with DAB is it is an old crappy codec that doesn't compress the audio as well as modern codecs do. In order to maximise profit, signals are encoded at very low bit rates and strangled bandwidth to squeeze more in. So you get the worst of both worlds perfectly reproduced crap audio and no way to in-situ upgrade to better codecs. Someone calculated that intelligible speech could, if tokenized, be sent down a 50bps channel. I.e imagine reduing it to text or sylalables sending that, and re synthesing a voice at the other end. I have done it on military systems at 600 bps[1] using a LPC-10 vocoder. Its far from telephony channel quality, and loses pretty much all character to the voice, but it is surprisingly intelligible so long as the speaker is trained to speak with discrete pauses between words. [1] which could then be sent with FEC and crypto layered on top over even poor quality HF channels using a radio modem. With frequency agile transceivers, it made a robust comms channel that was pretty much undetectable let alone recoverable to the wrong people, and nicely skirted round most ECM systems as well. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#46
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Mono Stereo
The issue with DAB is it is an old crappy codec that doesn't compress the audio as well as modern codecs do. In order to maximise profit, signals are encoded at very low bit rates and strangled bandwidth to squeeze more in. So you get the worst of both worlds perfectly reproduced crap audio and no way to in-situ upgrade to better codecs. Ever heard stations running the AAC+ or DAB2 codec at decent i.e. 112/128 K bit rates?.. -- Tony Sayer Man is least himself when he talks in his own person. Give him a keyboard, and he will reveal himself. |
#47
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Mono Stereo
In article ,
dennis@home wrote: You might as well say a CD played on the average radio FM station sounds nothing like it does at home. Due to the signal processing all broadcasters use. That is nothing to do with the FM medium. The difference in sound between CD and vinyl has nothing to do with the media too. Err, it has. Its down to the different processing needed to get a reasonable sound out of vinyl that they don't have to do on CDs. Different processing will of course make then sound different. But vinyl has inherent distortion - second harmonic? CDs being closer to the original but some still prefer the distortion in vinyl. Quite. Can make certain instruments sound more 'exciting'. -- *How's my driving? Call 999* Dave Plowman London SW To e-mail, change noise into sound. |
#48
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Mono Stereo
In article , The Natural Philosopher
scribeth thus On 22/04/2019 09:18, mm0fmf wrote: The issue with DAB is it is an old crappy codec that doesn't compress the audio as well as modern codecs do. In order to maximise profit, signals are encoded at very low bit rates and strangled bandwidth to squeeze more in. So you get the worst of both worlds perfectly reproduced crap audio and no way to in-situ upgrade to better codecs. Someone calculated that intelligible speech could, if tokenized, be sent down a 50bps channel. I.e imagine reduing it to text or sylalables sending that, and re synthesing a voice at the other end. Yes they IIRC call it a Vocoder used in mobile telephony and similar low rate applications.. It is completely bogus. But hey never mind the quality... look at the choice of stations.* Just that they all sound ****e. Even FM **** is now ****e as the Beeb doesnt bother sampling its own feeds internally at high rates. Can you be a bit more specific in that statement?.. -- Tony Sayer Man is least himself when he talks in his own person. Give him a keyboard, and he will reveal himself. |
#49
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Mono Stereo
In article ,
John Rumm wrote: With the possible caveat that in moving receiver applications, and high ambient noise environments, you *might* value the lack of fading etc as a benefit that outweighs the loss of absolute quality. Cople that with the fact that many people seem to be blissfully unaware of the lack of fidelity in their audio, and enough people put up with it without that much complaint. I do tend to laugh at those saying DAB is crap because it may not be transmitted in what they consider true stereo. Then go on about listing on a portable radio or car FM. When in a car, the decoder spends much of its time blending stereo to mono. Except in high signal strength areas. -- *I yell because I care Dave Plowman London SW To e-mail, change noise into sound. |
#50
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Mono Stereo
On 22/04/2019 11:46, Dave Plowman (News) wrote:
Not an inherent fault with DAB. The fault with DAB is you cannot upgrade the codec to anything acceptable by 2019 standards. So we're stuck with a poorly performing codec and then have bean counters forcing low bitrate streams. Bad codec and then constraining the bit rate is a recipe for ****ness. |
#51
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Mono Stereo
On Monday, 22 April 2019 11:27:54 UTC+1, The Natural Philosopher wrote:
On 22/04/2019 09:18, mm0fmf wrote: The issue with DAB is it is an old crappy codec that doesn't compress the audio as well as modern codecs do. In order to maximise profit, signals are encoded at very low bit rates and strangled bandwidth to squeeze more in. So you get the worst of both worlds perfectly reproduced crap audio and no way to in-situ upgrade to better codecs. Someone calculated that intelligible speech could, if tokenized, be sent down a 50bps channel. I.e imagine reduing it to text or sylalables sending that, and re synthesing a voice at the other end. .... sort of. The real world result is funny, someone described it IIRC as sounding like 2 robots fighting over a fag butt. Demo on youtube somewhere. NT |
#52
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Mono Stereo
On 22/04/2019 11:42, Dave Plowman (News) wrote:
In article , mm0fmf wrote: No. But DAB does sound ****e. Problem being having some expensive audio gear at home gets you used to stuff sounding good. The last car's original owner had fitted a £1200 audio upgrade which sounded fabulous on my high rate MP3s and CDs but the DAB was dire. FM sounded fine. Ages ago I put up some files of the same programme from DAB, FM and Freeview. Asked those who say DAB is **** to say which was which. Got the same results as using a pin. ;-) I'm sure you can find something at a semi-acceptable bit rate on DAB. But the stuff I listen to such as DAB R4 is in mono. On R4 FM I can listen to The Archers in stereo. I can hear people enter on the left, walk into the centre and exit stage right. It's really quite good. And on DAB that is all missing. Not a big issue when driving but I have a stereo system in the kitchen area. We spend a lot of time in there cooking and eating and we can listen to CDs in stereo, The Archers in stereo for example. And DAB is not an improvement but a significant downgrade in comparison. |
#53
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Mono Stereo
In article ,
mm0fmf wrote: On 22/04/2019 11:42, Dave Plowman (News) wrote: In article , mm0fmf wrote: No. But DAB does sound ****e. Problem being having some expensive audio gear at home gets you used to stuff sounding good. The last car's original owner had fitted a £1200 audio upgrade which sounded fabulous on my high rate MP3s and CDs but the DAB was dire. FM sounded fine. Ages ago I put up some files of the same programme from DAB, FM and Freeview. Asked those who say DAB is **** to say which was which. Got the same results as using a pin. ;-) I'm sure you can find something at a semi-acceptable bit rate on DAB. But the stuff I listen to such as DAB R4 is in mono. On R4 FM I can listen to The Archers in stereo. I can hear people enter on the left, walk into the centre and exit stage right. It's really quite good. And on DAB that is all missing. Not a big issue when driving but I have a stereo system in the kitchen area. We spend a lot of time in there cooking and eating and we can listen to CDs in stereo, The Archers in stereo for example. And DAB is not an improvement but a significant downgrade in comparison. That's not a fault of DAB, per se, but of how it is used. In my bedroom I get a rock steady DAB signal, while FM wanders in and out. -- from KT24 in Surrey, England "I'd rather die of exhaustion than die of boredom" Thomas Carlyle |
#54
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Mono Stereo
In article ,
mm0fmf wrote: Asked those who say DAB is **** to say which was which. Got the same results as using a pin. ;-) I'm sure you can find something at a semi-acceptable bit rate on DAB. But the stuff I listen to such as DAB R4 is in mono. On R4 FM I can listen to The Archers in stereo. I can hear people enter on the left, walk into the centre and exit stage right. It's really quite good. And on DAB that is all missing. Then don't use DAB. If you have a decent stereo system, it surely isn't your only choice? Not a big issue when driving Correct. Especially given an FM car radio will spend much of its time in mono anyway. but I have a stereo system in the kitchen area. We spend a lot of time in there cooking and eating and we can listen to CDs in stereo, The Archers in stereo for example. And DAB is not an improvement but a significant downgrade in comparison. DAB was specifically designed for reception on the move. -- *When the going gets tough, the tough take a coffee break * Dave Plowman London SW To e-mail, change noise into sound. |
#55
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Mono Stereo
On 22/04/2019 14:08, tony sayer wrote:
Even FM **** is now ****e as the Beeb doesnt bother sampling its own feeds internally at high rates. Can you be a bit more specific in that statement?.. Well funadmentally I was listening to classic FM on yer telly and banged over to a Beeb talk station. It was essentially band limited to what sounded like 4Khz. Sounded like AM radio....my assumption is that they dont actually carry high definition signals internally for some talk and local radio stations. -- "If you dont read the news paper, you are un-informed. If you read the news paper, you are mis-informed." Mark Twain |
#56
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Mono Stereo
On 22/04/2019 17:02, mm0fmf wrote:
On 22/04/2019 11:46, Dave Plowman (News) wrote: Not an inherent fault with DAB. The fault with DAB is you cannot upgrade the codec to anything acceptable by 2019 standards. So we're stuck with a poorly performing codec and then have bean counters forcing low bitrate streams. Bad codec and then constraining the bit rate is a recipe for ****ness. That was the beauty of FM seteroe, it didnt break FM mono... -- In a Time of Universal Deceit, Telling the Truth Is a Revolutionary Act. - George Orwell |
#57
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Mono Stereo
On 22/04/2019 19:49, mm0fmf wrote:
n R4 FM I can listen to The Archers in stereo. Good grief. Does anybody still lsiten to that **** at all? -- In a Time of Universal Deceit, Telling the Truth Is a Revolutionary Act. - George Orwell |
#58
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Mono Stereo
In article ,
charles wrote: That's not a fault of DAB, per se, but of how it is used. In my bedroom I get a rock steady DAB signal, while FM wanders in and out. BBC FM reception - except with a decent outside aerial - used to be truly dreadful over much of South London. Better since they added a fill in transmitter. -- *Remember: First you pillage, then you burn. Dave Plowman London SW To e-mail, change noise into sound. |
#59
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Mono Stereo
In article , The Natural Philosopher
scribeth thus On 22/04/2019 14:08, tony sayer wrote: Even FM **** is now ****e as the Beeb doesnt bother sampling its own feeds internally at high rates. Can you be a bit more specific in that statement?.. Well funadmentally I was listening to classic FM on yer telly and banged over to a Beeb talk station. It was essentially band limited to what sounded like 4Khz. Sounded like AM radio....my assumption is that they dont actually carry high definition signals internally for some talk and local radio stations. Well they do. bit then it depends on where its coded to whatever format they need... -- Tony Sayer Man is least himself when he talks in his own person. Give him a keyboard, and he will reveal himself. |
#60
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Mono Stereo
In article , mm0fmf
scribeth thus On 22/04/2019 11:46, Dave Plowman (News) wrote: Not an inherent fault with DAB. The fault with DAB is you cannot upgrade the codec to anything acceptable by 2019 standards. So we're stuck with a poorly performing codec and then have bean counters forcing low bitrate streams. Bad codec and then constraining the bit rate is a recipe for ****ness. Ever read about the AAC + or DAB 2 codec?... -- Tony Sayer Man is least himself when he talks in his own person. Give him a keyboard, and he will reveal himself. |
#61
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Mono Stereo
In article ,
tony sayer wrote: In article , The Natural Philosopher scribeth thus On 22/04/2019 14:08, tony sayer wrote: Even FM **** is now ****e as the Beeb doesnt bother sampling its own feeds internally at high rates. Can you be a bit more specific in that statement?.. Well funadmentally I was listening to classic FM on yer telly and banged over to a Beeb talk station. It was essentially band limited to what sounded like 4Khz. Sounded like AM radio....my assumption is that they dont actually carry high definition signals internally for some talk and local radio stations. Well they do. bit then it depends on where its coded to whatever format they need... Turnip probably didn't realise it was a phone in. ;-) -- *Give me ambiguity or give me something else. Dave Plowman London SW To e-mail, change noise into sound. |
#62
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Mono Stereo
On 23/04/2019 15:49, tony sayer wrote:
In article , mm0fmf scribeth thus On 22/04/2019 11:46, Dave Plowman (News) wrote: Not an inherent fault with DAB. The fault with DAB is you cannot upgrade the codec to anything acceptable by 2019 standards. So we're stuck with a poorly performing codec and then have bean counters forcing low bitrate streams. Bad codec and then constraining the bit rate is a recipe for ****ness. Ever read about the AAC + or DAB 2 codec?... Yes. Can I upgrade the built my car audio system that only has DAB to DAB+? No. |
#63
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Mono Stereo
In article ,
mm0fmf wrote: Ever read about the AAC + or DAB 2 codec?... Yes. Can I upgrade the built my car audio system that only has DAB to DAB+? No. You find the audio quality of DAB unacceptable in your car? -- *You're never too old to learn something stupid. Dave Plowman London SW To e-mail, change noise into sound. |
#64
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Mono Stereo
In article , mm0fmf
scribeth thus On 23/04/2019 15:49, tony sayer wrote: In article , mm0fmf scribeth thus On 22/04/2019 11:46, Dave Plowman (News) wrote: Not an inherent fault with DAB. The fault with DAB is you cannot upgrade the codec to anything acceptable by 2019 standards. So we're stuck with a poorly performing codec and then have bean counters forcing low bitrate streams. Bad codec and then constraining the bit rate is a recipe for ****ness. Ever read about the AAC + or DAB 2 codec?... Yes. Can I upgrade the built my car audio system that only has DAB to DAB+? No. Yes true but i don't think that AAC was around at the time.. Around the early 90's when DAB was being formulated.. -- Tony Sayer Man is least himself when he talks in his own person. Give him a keyboard, and he will reveal himself. |
#65
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On 25/04/2019 09:35, tony sayer wrote:
In article , mm0fmf scribeth thus On 23/04/2019 15:49, tony sayer wrote: In article , mm0fmf scribeth thus On 22/04/2019 11:46, Dave Plowman (News) wrote: Not an inherent fault with DAB. The fault with DAB is you cannot upgrade the codec to anything acceptable by 2019 standards. So we're stuck with a poorly performing codec and then have bean counters forcing low bitrate streams. Bad codec and then constraining the bit rate is a recipe for ****ness. Ever read about the AAC + or DAB 2 codec?... Yes. Can I upgrade the built my car audio system that only has DAB to DAB+? No. Yes true but i don't think that AAC was around at the time.. Around the early 90's when DAB was being formulated.. 80s https://www.bbc.co.uk/news/10569231 Then AIUI no one in the UK had the guts to say "oops!" -- Robin reply-to address is (intended to be) valid |
#66
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In article , Robin
scribeth thus On 25/04/2019 09:35, tony sayer wrote: In article , mm0fmf scribeth thus On 23/04/2019 15:49, tony sayer wrote: In article , mm0fmf scribeth thus On 22/04/2019 11:46, Dave Plowman (News) wrote: Not an inherent fault with DAB. The fault with DAB is you cannot upgrade the codec to anything acceptable by 2019 standards. So we're stuck with a poorly performing codec and then have bean counters forcing low bitrate streams. Bad codec and then constraining the bit rate is a recipe for ****ness. Ever read about the AAC + or DAB 2 codec?... Yes. Can I upgrade the built my car audio system that only has DAB to DAB+? No. Yes true but i don't think that AAC was around at the time.. Around the early 90's when DAB was being formulated.. 80s https://www.bbc.co.uk/news/10569231 Then AIUI no one in the UK had the guts to say "oops!" 80's and part 90's and original work prolly before that but in all fairness the basic idea behind DAB is OFDM modulation which offered several advantages over FM especially for mobile reception. It was not upgradable to another better codec but oddly enough the modulator and multiplexer we have on our local trial DAB service MUX can handle standard DAB and DAB+ the DAB Plus we have had several reports on is performing better reception wise than standard DAB .. FWIW... Then the idea of bit reduction came about no one saw that forthcoming it seems till it got here.. -- Tony Sayer Man is least himself when he talks in his own person. Give him a keyboard, and he will reveal himself. |
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