VU Meter on LiveStream

This is a Legacy Page and will no longer be updated

New: DCI has stopped its video streaming and VU meter service in favor of the far superior NorCal audio streaming and VU meter Broadcastify will continue for now.  This page is now a legacy page and will ultimately be dropped from this website.

New: NorCal's Streaming Audio and VU Meter

AGC UPDATE:  Gen 1 MotoTRBO radios running R01.12.02 firmware can now run with Digital AGC enabled as the radio now handles audio much better than the past 4 years firmware versions.


The LED VU bar meter shown in DCI's "Livestream Feed" provides an objective view of the range of talkgroup audio levels on DCI 1, DCI 2, Bridge 2, Tac 310-2 and Comm 1, (Worldwide and North America talkgroups by net schedule or other random times).  The target range is the 6 yellow bars  but 1 red square is acceptable on peaks only.

The meter is adjusted so that reasonable audio (no piercing audio, no distortion and breath puffs minimized) is likely when your average audio falls within the yellow range.  This set-up provides a more complete "picture" of all audio conditions.  More details below on how to test your audio. The 4 reds are visible and they show as squares to to more easily distinguish the colors. The peak audio level is held for 1 second.  The bottom 5 greens are not visible online.

If you are using this VU Meter to monitor or adjust your audio, you should keep in mind the following for best use of the tool:

Announce on the air that you are conducting an audio test, invite anyone to listen and comment.  Mention audio test as it will key other listeners that it's audio and not RF or other system testing. They may then jump in, help you and have a more critical ear for feedback to you if they know ahead of what you are about to do.

Use your normal voice, normal position, under normal conditions.  Sounds easy but it is not.  Think about how other people use cell phones, they talk louder when unaware of the distraction they are causing.  Most people will speak softer when they are aware of the noise they are creating or in this case when the OTA level may be offensive.  Most users will again, speak softer when advised of their hot audio but it will creep back up when they forget about it later.  So try to resist that temporary reaction.  You could have your friends monitor your audio at random times and report back to you later as to where your audio falls when you are not thinking about your audio levels.  Most users tend to be offended, even if they don't indicate it.  So try to be gentle and diplomatic.  But a temporary solution by saying that you will talk softer or further from the mic IS NOT THE ANSWER.  You must reprogram for your voice and style or you will fall back into that old method of speaking to your radio and continue to violate acceptable levels of audio as well as the clarity of your speech.  This cannot be emphasized enough!

The target is to hit the yellow bars without going into the red, paying attention to the average range of the bars.  1 red square is OK but no higher.  Anything else should merit your attention or correction.  This is different from a normal VU level in other applications but was done to keep it visually simple, just hit the 6 yellow segments on average but never into the reds.  Greens only are too low but better than hitting the reds.

 The sample at left shows 4 of 5 yellows which is essentially perfect.

We suggest saying something like, "This is K6HOT, VU Audio Test 1, 2, 3, 4, 5".  To "exercise" your audio, you might say "4" several times; long and sustained as it provides a better view of the bars and tends to be the hottest audio in the number string.  Remember the delay, you should have at least 5 seconds before  your voice makes it out of the stream. 

Turn your local audio up and listen closely for syllables that confuse the vocoder as well as breath puffs across the mic.  These are points that cause the most grief for the listeners when your overall audio is too hot.  Even when audio is in the yellows, the vocoder may still have trouble processing the sounds so listening closely should help you determine if you should adjust your position relative to the mic on the radio.

AGC Issues

We are finding that "AGC off" with various levels of gain published on our audio levels page is  working out well if you use the MARC guide as the starting point to adjust your own levels. This VU meter will enable you to see where your levels fall in normal circumstances.  Further it appears that the Gen 2 radios now handle audio better by default, if AGC is enabled.

TRBO audio has an extremely wide dynamic range.  AGC does limit that range as it should most of the time.  It's those times that it does not is what has caused all the interest in audio levels. 

The dynamic range of the meter is -20 to +3dB in twenty steps and this actually is closer to the TRBO dynamic range.  Just watch the bars as you listen to yourself or others in conversation.  The base line volume setting is so that a DTMF 5 will hit the 2nd red square (try sending yourself TT5 direct to another radio-it is loud!).  The VU meter sits right on speaker audio out through a 8 ohm/10k ohm isolation transformer, the volume is has been set at the exact same level since the beginning of the project (2012).  Otherwise, the audio is not conditioned as it is feed to the LED array which as a 31 hz to 16 Khz native response.

The streaming servers clients are fed conditioned audio to narrow the wide dynamic range of TRBO so that it can be fed to the streaming services without hitting their level ceilings (distortion).  The audio is compressed 3 to 1 when levels hit +3 dB (1 red bar).  This is an effort to keep the TRBO audio from overdriving and distorting the audio that is sent to the streaming server clients.  This is made more difficult as the lower audios actually need to be boasted and that is limited to only 3 db with the current hardware.  But the lower audios NEVER produce that nasty piercing noise and distortion, so the emphasis is on clean audio rather than high to hot audio.

We are hopeful that more people will try to target their audio into the 6 yellow bars.  TRBO has a very wide useable dynamic audio range with most of the problems occurring at the high or hot end of the scale.  If more of us can stay out of the 4 reds, we will have cleaner audios and fewer folks diving for the volume control when the radio barks that piercing audio while the softer talkers are more likely to be heard as the speaker audio can be turned up.  But the hot talkers should throttle back.