P25 Audio

[Gezelle007]

Does anyone enjoy the sound of P25 audio over analog? Because listening to some youtube videos and some live feeds from the RR- In my opinion I would rather have analog.

Its almost like comparing it to newer HD TV's vs the older. If you go in to Frys or Best Buy or something and check them out, they are so high definition and clear that its TOO clear. The movement is to fluid. Its so real looking that it looks fake.

This is the same feeling I get when I listen to digital p25 audio. I'd like to hear your opinions on the topic.

 

[KD0NDO]

p25 is nice until it garbles. an other hand Ithink that it makes people sound the same (to some extent)

 

[12dbsinad]

I think P25 audio sucks myself. I'd much rather listen to analog. P25 is very monotone, has no fidelity which is why it seems like everyone sounds the same.

 

[unixfreak0037]

Yeah, seems like there's been some other discussions regarding this issue. I live in Northern Kentucky near Cincinnati. Cincinnati PD sounds *horrible*. KSP is P-25, they sound OK, but Boone Co, KY is still analog, and not only do they sound the best, they also have the greatest range.

I was at the in-laws last night in Butler Co., Ohio and tried listening to BRICS (Butler Co Ohio's digital system) and it was spotty at best. But I could still pick up all three Northern Kentucky counties perfectly.

Maybe it's just that scanner radios don't tune in the digital stuff as well as the transceivers that are specifically built for it. But it seems that the digital stuff just isn't nearly as good.

IMHO.

John

 

[Gezelle007]

p25 is nice until it garbles. an other hand Ithink that it makes people sound the same (to some extent)

Yep. That is pretty much what Ive been hearing, currently there are only a couple p25 networks with in my range, but I don't have a digital scanner yet so Ive been relying on feeds and youtube vids. Listening to both, I do hear the garbles and like most people have said, it does make people sound the same. And their are some moments when you can hear the simulcasting part of hit, that periodic static here and there.

There is a video, YouTube - Motorola XTS-5000 Radio Chatter, which shows and xts5000 monitoring an LAPD channel. For the most part it seems alright. But in my opinion I still don't like it.

 

[grem467]

you are seriously determining if you like a certian audio sound by a YOUTUBE video?

 

[gewecke]

P25 audio was NEVER supposed to be high fidelity from the start.
n9zas

 

[Gezelle007]

you are seriously determining if you like a certian audio sound by a YOUTUBE video?

No. Not really, like I said earlier, I have listened to live feeds of it. When it worbles, it sounds terrible.

 

[ssd]

the p25 audio on my astro saber is so fine. on vhf. i can here it clear. and no fade out. it works well on a radio. a scanner well u hate it. and if u had the same xts as the cops. have. u would see how well it works.

 

[canav844]

No. Not really, like I said earlier, I have listened to live feeds of it. When it worbles, it sounds terrible.

Live feeds are heavily compressed and with both P25 and DSTAR I have found they do not sound the same as the sound coming out of the radio, same goes for analog to some extent. Unless you've heard it directly from the radio it's really not a fair comparison.

When we switched from analog to P25 the automatic gain control wasn't dialed in yet, quiet people were much quieter and someone screaming into the mic on the side of the highway wasn't muffled, and that took some getting used to. But I've grown to like it. I've even heard stories of some using the portables to be looking over their shoulder for who was talking because the P25 sounded so natural they didn't think it was the radio.

It's different, some people like it, but most resist change; there are still some HAM radio circles out there that would scoff at using any mode other than CW. Change takes time to get used to, there's benefits and weaknesses to P25, but outside of the fire service (and from what I heard adjustments are being made with Phase II to suppress those concerns) with a well designed network P25 will preform at least equally well if not better than analog.

It also allows agencies using multiple trunk sites to have the radios automatically associate with the nearest tower instead of manually having to make the switch, you always get the unit ID without having to hear MDC1200 beeps, if a user keys up when the system is busy, instead of doubling you get feedback that the system is busy, with emergency functions setup a user can break into a conversation when the system is busy, and all radios on that channel will display who has hit their emergency button so others in the area can respond accordingly.

While P25 is not an end all be all of radio by any means it does provide some enhanced features with decent sound quality, in my experience (using a variety of P25 Motorola radios as well as Uniden scanners) and opinion.

 

[Baylink]

One other thought: audio going through a P25 system is compressed. Audio going out a feed is compressed. The compression systems are *different*, and even going back to analog in the middle does not guarantee that the first compression won't leave artifacts in the audio which would be ok if you were listening to it first hand, but will just kill you if you're listening to it over a feed.

HT vs scanner, of course, is a different issue, probably having much to do with $300 scanner vs $6000 HT.

 

[jackj]

What artifact is a result of compression Baylink? ALL commercial broadcast stations compress their audio to some extent and the only result is a reduction in dynamic range, which is the goal of audio compression. As for the compression systems being 'different', well they may have different triggering thresholds and target levels but they all produce the same results and work in very similar ways.

 

[Baylink]

Jack, you're confusing *analog* compression, which adjusts the level of the analog signal before it enters the transmitter, and has no artifacts in the sense in which I mean them here...

with *digital* compression, which -- for voice-only channels -- works by *throwing away* parts of that analog signal, to get something which is easier to compress digitally... in *theory*, throwing away parts which you don't actually notice.

*You* don't notice them, but some other digital audio codec can, and often will; the results of expanding and recompressing digital audio *or* video are well known, and often not what you'd like.

VSELP, CELP, ABME and IMBE (as well as Speex) are all codecs which fall in this category; the artifacts they leave in the reconstituted analog spectrum make things quite a bit less effective for any additional compression-digitization applied to that analog stream.

See

https://secure.wikimedia.org/wikipedia/en/wiki/Transcoding

and also

https://secure.wikimedia.org/wikipedia/en/wiki/Digital_generation_loss#Digital_generation_loss

for more on this.

 

[jackj]

Sorry about that Baylink, you said the audio was compressed and that created the artifacts. I naturally thought you meant that the audio was compressed, not the data. Yes, you are correct in that the data is compressed before it is transmitted and that can screw up some D to A converters. But that is a completely different type of compression and is not, technically, audio compression. Most units also use some audio compression to reduce the dynamic range before the audio is sent to the A to D converter.

 

[lspdunsure]

p25 audio be or bad audio???? p25 stinks!

the thing that people are doing is that they are comparing controlled audio (studio,tv, controlled environmental ) application audio to the real thing outside world audio. it is gonna get someone killed !!!motorola and others have been improving on it but it is still a long way from being safe in the police and fire industry.. the way that they process the audio is not good when applied to the outside noises like wind noise, traffic and breathing through a air pack. it sounds great in a studio environment but not in the outside world.i think in the long run, someday they will get it good and sounding like the quality of analog audio is and has been for many years.
the next biggest deal is with the reduced radio coverage area problems. when you get into a fringe area of radio coverage, like in buildings, tunnels and cars, analog will at least give you a scratchy signal and digital will give you none! for a swatt cop on the floor in the basement trying to talk , this is NOT a option.!!there is a ton of examples or bad digital audio stuff out there, just pick up any fire or police magazine and read.... motorola and the government politic things are pushing this technology too soon. stick with analog for now and wait for the manufactures to figer it out.
if your a cop or fireman, be careful..........

 

[GSPD]

I'll take analog over digital any day. I still can't get used to the uneven audio levels, squeaks, beeps and dropouts associated with it. We currently use XTL2500's and XTS2500's. I'd love to see analog return, but we know those days are long gone.

 

[12dbsinad]

I'll take analog over digital any day. I still can't get used to the uneven audio levels, squeaks, beeps and dropouts associated with it. We currently use XTL2500's and XTS2500's. I'd love to see analog return, but we know those days are long gone.

Well, i have heard of agencies return to analog after putting up a very big fit (which i cant blame them) but usually on smaller systems. I just dont see what the hype is about about P25. At this point, analog is like the round wheel... hard to re-invent it. maybe some day yes, but at this point in time it just seems to fill wallets, at the users expense. As of my opionion for right now, analog wins hands down.

 

[Gezelle007]

Well, i have heard of agencies return to analog after putting up a very big fit (which i cant blame them) but usually on smaller systems. I just dont see what the hype is about about P25. At this point, analog is like the round wheel... hard to re-invent it. maybe some day yes, but at this point in time it just seems to fill wallets, at the users expense. As of my opionion for right now, analog wins hands down.

I agree. Whats the point of changing something that works fine already. People seem so eager to jump right into the new technology of things without waiting awhile for it to get better after revisions.

Anyways, has anyone put a p25 channel into an analog scanner, I just want to know what it sounds like so if I do pick it up randomly Ill know what it sounds like. I'm assuming it sounds like a hum sound with no audible voice correct?

 

[canav844]

the next biggest deal is with the reduced radio coverage area problems. when you get into a fringe area of radio coverage, like in buildings, tunnels and cars, analog will at least give you a scratchy signal and digital will give you none! for a swatt cop on the floor in the basement trying to talk , this is NOT a option.!!there is a ton of examples or bad digital audio stuff out there, just pick up any fire or police magazine and read.... motorola and the government politic things are pushing this technology too soon. stick with analog for now and wait for the manufactures to figer it out.
if your a cop or fireman, be careful..........

Our officers went from having to get into their squad and drive out of the jail sally port to get their mobile to reach our repeaters to being able to get in through their portables, it all comes down to system design and I've seen analog out reach digital and digital outreach analog, it's still a matter of RF getting from point A to point B.

Anyways, has anyone put a p25 channel into an analog scanner, I just want to know what it sounds like so if I do pick it up randomly Ill know what it sounds like. I'm assuming it sounds like a hum sound with no audible voice correct?

P25 sounds alot like a modem (or similar to a Moto control channel) when picked up by an analog radio, it's got a different characteristic to it that I've been able to tell it was P25 a few times, but I can't describe it well enough. I'm sure there's probably a recording on youtube somewhere.

 

[jackj]

Our officers went from having to get into their squad and drive out of the jail sally port to get their mobile to reach our repeaters to being able to get in through their portables, it all comes down to system design and I've seen analog out reach digital and digital outreach analog, it's still a matter of RF getting from point A to point B.

I think you will find that the difference between your old analog system and your new digital system is location, location, location. Your analog system probably had only one base station/repeater. Your new digital system will have a number of stations, all interconnected with each other and your dispatch You might even have one at the jail. If your analog system had been engineered and installed the same way, it would OUT PERFORM the digital system.

Digital has one drawback that it will NEVER be able to overcome, there isn't any redundancy to the information it transmits. Forward Error Correction (FEC) is not the same as redundancy. If you loose 50% of the transmission with digital, you don't have ANY communication. Analog can give dependable communication and still loose over 80% of the transmission.