I recently got some Dahua IPC-HDW5442TM-AS cameras. Previously I used
Amcrest cameras. I was quite disappointed that the audio sample rate on the new Dahua camera was limited to 8k instead of supporting 8k and 16k as the Amcrest cameras do. However, I discovered that if I switch the Dahua camera to use the AAC format, the list of supported sample rates expands all the way up to 64k (48k is the normal sample rate used for most media nowadays). I was worried that
Blue Iris wouldn't be able to use the audio stream while in AAC mode, but it does fine. Judging by the sound quality, Blue Iris isn't using the camera's AAC bitstream (which has a crazy low bitrate that sounds garbly), but the audio comes through quite well, and at the full sample rate. Therefore, to get the best audio quality on at least some Dahua cameras:
- In the camera's audio settings, make sure that Noise Filter is turned off.
- In the camera's audio settings, check your available Sampling Frequency and set it to the highest option. 8k is telephone quality. 16k is slightly better. 48k is preferable.
- Try changing the Encode Mode to AAC and see if your Sampling Frequency will now go higher. If so, stay with AAC. Otherwise use G.711A.
- If you're using Blue Iris, try setting its camera audio format to 16-bit PCM (Camera settings -> Video -> Configure -> Audio -> Format).
- I have replaced the internal microphone on several of these Amcrest/Dahua cameras with great results. Since the camera's internal preamplifier is quite noisy, the point is to find the most sensitive microphone possible. These microphones are among the best available (soldering required).
- Drill the microphone hole out on the camera housing to get rid of the shrill, tinniness of the sound. Depending on the camera's location, you may need to consider replacement weatherproofing options for the microphone. I like to drill the hole to the diameter of the microphone element, placing the element in the back of the "tube" of the camera housing, using thermal glue from behind to hold it in place, and then filling the front of the tube with a small chunk of earpiece foam from old headphones to reduce wind noise and keep stray, airborne water droplets from hitting the microphone.
If you do all the above, it will be a night and day difference in audio quality and sensitivity compared to how the camera originally behaved! Maybe sometime I'll have a demo to demonstrate what's possible.