I've been using your program for some time. Here are my suggestions:

1) Multichannel with individual squelch would sure work for me, and
quite frankly it would be the only way to get me to pay for the
software. I'm sure there is a pro-audio multitrack file format.

2) Some sort of periodic auto-save function is needed. I often record
in the field and don't always catch the notebook battery meter
indicating a low function.

Note that I always record in PCM and then convert to compressed audio
later. This has a few advantages. One, I can "normalize" the audio in
soundforge prior to compressing it. If you adjust the audio level of a
compressed file, I believe it gets compressed twice. Second, I I can
take individual bits of audio and boost the level of just that section.
Audio levels are all over the map if you record military air. Third,
the filters work better on PCM. Often I need to notch 400hz and 1200Hz
from aircraft generators.

Now this leads to another featu

3) Dump the auto-clip scheme. Sixteen bits of audio is plenty of
headroom. Encourage the user to leave a bit of headroom when recording.
Then for each segment of audio, normalize it. This will adjust for
variations in audio level from radio to radio. This implies you will
need a buffer for the audio segment, and the ability to simultaneously
normalize one segment of audio while still recording the next segment.

Here is an idea for another product. These flash recorders (Iriver,
Creative, etc) are getting quite cheap, but they still haven't mastered
the idea of a vox. A program that would take a file from a flash
recorder and strip out the silence would be useful.

Ultimately, the audio recorder belong in the scanner itself. The
manufacturers are idiots for not doing so. It would have the advantage
that the audio segment could be tagged with frequency, time, talk
group,etc.You could scan multiple frequencies and then reassemble all
the audio segments using the tags. Uniden and GRE just can't think out
of the box. For P25, you could just store the digital audio.

I think these ideas are some of the best I've heard so far.
Especially the auto-normalize. That seems so useful and
after all these years, I never though of that one and no one
else has suggested that.


On 4 Aug 2005 23:05:31 -0700, wrote:

I've been using your program for some time. Here are my suggestions:

1) Multichannel with individual squelch would sure work for me, and
quite frankly it would be the only way to get me to pay for the
software. I'm sure there is a pro-audio multitrack file format.

2) Some sort of periodic auto-save function is needed. I often record
in the field and don't always catch the notebook battery meter
indicating a low function.

Would auto-save to a new file name (say, using a sequence
number) be acceptable instead of re-opening the previously
written file?

A .wav or .mp3 file has to be closed before it's considered
to be safely stored. That means that it cannot be appended
to without a lot of potential problems. If the format is raw
data with no headers (like the .RAW format used by Sound
forge) then it would be easy to append after closing the
file. Maybe I should consider adding a .RAW format for that
reason.

But IMHO, it's not safe to update the headers (which is
necessary to append more audio) of the .WAV or .MP3 file
that's already been closed because the computer could die in
the middle of the update and that might leave the file
crippled. Manipulating the previously saved headers can
invite other problems too, such as adding a lot of disk
seeking and CPU time to reopen the file for appending after
it's already been closed. Appending more audio requires a
read-scan of the entire file in order to locate and change
the existing audio (RIFF) headers.

Note that I always record in PCM and then convert to compressed audio
later. This has a few advantages. One, I can "normalize" the audio in
soundforge prior to compressing it. If you adjust the audio level of a
compressed file, I believe it gets compressed twice. Second, I I can
take individual bits of audio and boost the level of just that section.
Audio levels are all over the map if you record military air. Third,
the filters work better on PCM. Often I need to notch 400hz and 1200Hz
from aircraft generators.

Now this leads to another featu

3) Dump the auto-clip scheme.

If you're talking about the Scanner Recorder anti-clip, that
has to do with preventing the audio from being clipped off
at the beginning the way a mechanical VOX recorder does.
That works by keeping the last 10 MS of audio in a buffer
and drawing from that buffer whenever the VOX is opened to
prevent that pop sound. Like if it records a person saying
the word "testing" and it ends up sounding like "esting".

Sixteen bits of audio is plenty of
headroom. Encourage the user to leave a bit of headroom when recording.
Then for each segment of audio, normalize it. This will adjust for
variations in audio level from radio to radio. This implies you will
need a buffer for the audio segment, and the ability to simultaneously
normalize one segment of audio while still recording the next segment.

Here is an idea for another product. These flash recorders (Iriver,
Creative, etc) are getting quite cheap, but they still haven't mastered
the idea of a vox. A program that would take a file from a flash
recorder and strip out the silence would be useful.

Sound Forge can do that using Auto-Region I think.

Ultimately, the audio recorder belong in the scanner itself. The
manufacturers are idiots for not doing so. It would have the advantage
that the audio segment could be tagged with frequency, time, talk
group,etc.You could scan multiple frequencies and then reassemble all
the audio segments using the tags. Uniden and GRE just can't think out
of the box. For P25, you could just store the digital audio.

I really appreciate the great ideas! Thanks.

I think of clipping as in reaching the maximum audio level, not
clipping off a bit of sound. However, I can see why someone would think
that way. I could have sworn the audio sounded more distorted with the
clipping turned on, but it could be I was doing something else wrong at
the time.

Since I don't know the details in file format, I obviously have to
leave autosave up to you.However, the notion of RAW sounds good to me.
Even notebook HDs are big enough not to need compression for the local
file. I only compress for internet use.

Another idea might be an intentional user definable :"snip" at the end
of each segment of audio. Some scanners have an annoying squelch tail
that would sound better snipped off.

Lastly, perhaps the scanner recorder could be set up to either process
"live" audio or audio files. This way someone could record audio with
the Irver or Create Nuvo, then remove the gaps later. I've recorded
audio in locations where it really isn't all that handy to bring a
notebook computer.

These were done with the scanner recorder and a notebook computer.
http://www.lazygranch.com/red_audio.htm

This is a typical file with all the warts of mil air in field
recording:
http://www.lazygranch.com/sound/redf...pm308p6mp3.wav
Everything is simplex with constant changing distances. With AM, weak
signals really sound bad, so MP3 recording before processing just
doesn't work. The newer files I've done have been encoded in ADPCM. Not
all that dense, but much better quality.

http://www.lazygranch.com/sound/jane...v_07212005.wav

Here the planes on the ground are very wek since I don't have line of
sight. The audio would sound quite poor in mp3, but is passable in
ADPCM.

On 5 Aug 2005 17:33:14 -0700, wrote:

I think of clipping as in reaching the maximum audio level, not
clipping off a bit of sound. However, I can see why someone would think
that way. I could have sworn the audio sounded more distorted with the
clipping turned on, but it could be I was doing something else wrong at
the time.

It's my fault for not providing much help to people on what
it is. Funny thing is that when I put a switch in to turn
the anti-clip off, I couldn't tell the difference in how it
sounded. No moving parts responds real quickly. I never
needed it in the first place.

Since I don't know the details in file format, I obviously have to
leave autosave up to you.However, the notion of RAW sounds good to me.
Even notebook HDs are big enough not to need compression for the local
file. I only compress for internet use.

Another idea might be an intentional user definable :"snip" at the end
of each segment of audio. Some scanners have an annoying squelch tail
that would sound better snipped off.

Will add that to the list.

Lastly, perhaps the scanner recorder could be set up to either process
"live" audio or audio files. This way someone could record audio with
the Irver or Create Nuvo, then remove the gaps later. I've recorded
audio in locations where it really isn't all that handy to bring a
notebook computer.

A utility tool maybe to do that. It's just that I'm not sure
how to implement it yet. It currently uses "push" logic to
push the audio downstream from the capture to the file.
Processing a file is reversed. It's "pull" logic. It might
be too confusing for me to put both together in one program
just yet.

These were done with the scanner recorder and a notebook computer.
http://www.lazygranch.com/red_audio.htm

This is a typical file with all the warts of mil air in field
recording:
http://www.lazygranch.com/sound/redf...pm308p6mp3.wav
Everything is simplex with constant changing distances. With AM, weak
signals really sound bad, so MP3 recording before processing just
doesn't work. The newer files I've done have been encoded in ADPCM. Not
all that dense, but much better quality.

http://www.lazygranch.com/sound/jane...v_07212005.wav

Here the planes on the ground are very wek since I don't have line of
sight. The audio would sound quite poor in mp3, but is passable in
ADPCM.

You have a great web site. I really enjoyed exploring. Will
be going back there to check out more things. I found the
plane wreck expeditions very interesting and wish I were
able to accomplish that kind of expedition. It must've been
great fun to go to those sites! It reminds me - a couple of
years ago a friend who I met at the RC flying field (Morgan
Hill) had a hanger full of plane parts and other junk. Up on
the top level inside the hanger was a full sized, wreck of a
WW2 spitfire with the tail numbers on it. I went on the
internet and found lots of pics of that plane and made
contact with someone in the UK who had a database of many
planes and their dispositions. He had that plane in his list
as "missing" and I was happy to tell him that I found his
missing plane in the Morgan Hill area south of San Jose. He
was real happy to be able to update his listing. It was a
fatal crash of a pilot flying it between air-shows. He was
enroute to somewhere in Nevada and had a full speed cruising
impact into a hill due to poor vis. The entire (or most of
it) plane was in the hanger and it was really messed up
badly.

BTW: You have my email from the Scanrec about page. Feel
free to email any time if you want to talk about it more.

Anyway, thanks a lot for all the ideas. I appreciate it!!

On Fri, 05 Aug 2005 00:10:42 -0700, Dave said in
alt.radio.scanner:

But IMHO, it's not safe to update the headers (which is
necessary to append more audio) of the .WAV or .MP3 file
that's already been closed because the computer could die in
the middle of the update and that might leave the file
crippled.

Same problem text editors have. You update a copy of the file,
deleting and renaming only after a successful update. (Which is why
Word leaves ~garbage.doc files around.)

Manipulating the previously saved headers can
invite other problems too, such as adding a lot of disk
seeking and CPU time to reopen the file for appending after
it's already been closed. Appending more audio requires a
read-scan of the entire file in order to locate and change
the existing audio (RIFF) headers.

My computer can do video decode at 150fps or better, while streaming
audio to the web. I don't think CPU power is something we have to
worry about with files or audio any longer.

Unlike Zombie Wolf, I don't have any pressing projects at the moment,
so if you'd like a collaborator, let me know.