wednesday I made a recording and got the audio from the audio guys. the recording was edited for an impression summary using two audio sources: the vmix recorded audio and the master recording from one of the camera's.

one of my editers noted a high pitched shreeking noise in some parts of the edited video. I checked and found that the vmix recording is the source of this. on the exact same part recorded on the camera which was input to vimix for the recording the audio track is clear from this noise.

Does anybody ever noticed something like this before?

I used the latest vmix build, with input through capture cards sdi 720p50 straight from my canon xa25 sdi output. I compared the original master with the vmix recording.

ps for parts that I edited I use the multi cam track and select the audio from the master. the master has two channels, left and right where left is recorded slightly over -10 db mark and right recorded slightly under -10 db mark on cam. this way I always have a good channel to use. in vmix the stereo is switched to seperate channels. In case i need to select one of the channels I just reduced the channel i don't want. in this case i used both channels mixed to the recording but flattened to dual mono.

cheers stefan

I can provide a sample in case this is needed of a part of the recording using master and vmix recorded sound.

after discussing the issue with Martin and doing some tests the problem seems to be in the acc compression settings with lower bitrate. so as a general rule it is better to set othis on max bitrate or 192 in recording settings when using mp4 recording.

also martin pointed out that recording as seperate mono might increase some extra noise.

maybe a feature request would be to provide higher bitrates for recording audio. I proces in post to mp4 with audio on 320 kbps... for the file size theres not much difference.

stefan