1. Lowering CPU

1.1 Avoid audio resampling

To avoid audio resampling, the SIP clients connecting to a bridge have to use a codec with the sample rate, channels and bits per sample as the "pivot settings". For more information, check here.
tip: In you configuration file, enable codecs with same settings as the pivot.

1.2 Only record sessions if needed

Do not enable recording if it’s not important to you or use *.avi container which consume less CPU than *.mp4 (because of AAC encoder from libfaac).

1.3 Use common video codec

All SIP clients with the same video codec will share a single encoder. Try to use common video codec for all clients. For example, if you have two clients, A and B, with A supporting both H.264 and VP8 and B only H.264 then, you should make sure that A will offer H.264 with highest priority. For more information, check here.
tip: In your configuration file, enable a single video codec if you cannot control the SIP clients.

1.4 Use 2d audio mixing

Enable 2D audio mixing instead of 3D.

1.5 Lower mixed video size and fps

If you have a weak CPU then, consider using a reasonable video size (e.g. VGA) and fps (- 30).

1.5 Multi-threading and ASM

Make sure to enable YASM and pthread when building FFmpeg, x264 and VP8.

2. Lowering bandwidth

• Use "slow" motion rank (see here)
• Use small mixed video size (see here)
• Set the maximum upload and download bandwidth (see here)
• Use small video frame rate (see here)

tip: To test your available bandwidth, we recommend http://www.speedtest.net/.
tip: To check bandwidth usage, we recommend iftop.

3. Improving audio quality

• Use Opus (or G.722) audio codec if supported by the SIP clients (see here).
• Avoid audio up-sampling and down-sampling (see here).
• If the "pivot settings" use a sample rate (SR) equal to S then, try to use codecs with a SR equal to "S << n" or "S >> n".

4. Improving video quality

• Use Google Chrome as SIP client (check our WebRTC demo client at http://conf-call.org/).
• Enable "Zero-Artifacts" feature (see here and here)
• Use a client supporting something close to 16/9 video size to avoid stretching issues
• Avoid video up-sampling and down-sampling

5. Lowering recorded video file size

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