This page covers the three settings that decide picture quality and how hard the machine has to work. It is also where the one genuine trap in this part lives: what the total bitrate actually means.
Encoder
Settings → Outputs → Encoder.
| Choice | |
|---|---|
| x264 (software) | Encodes on the processor. Available everywhere, best quality per bit, and by far the most work for the machine. |
| Hardware encoders | Whatever the machine’s graphics card offers — NVIDIA, Intel or AMD. They appear in the list by themselves. |
Use the hardware encoder if there is one. It takes the encoding off the processor that is already busy rendering your playouts, and on a machine running two lines that difference is the difference between working and dropping frames.
x264 is the fallback for machines without a usable card, and the choice when quality at a low bitrate matters more than processor load.
Output size
The size the stream is sent at: the canvas size or a step below it, always in the canvas’s shape. Scaling down for the stream while composing at full size is normal: 1920×1080 canvas, 1280×720 stream.
Smaller costs less bitrate and less encoding. There is no point sending a size larger than your bitrate can carry — that is how you get a smeared picture on movement.
Total bitrate, and the trap
Total bitrate is video and audio together — what your server allows. The audio is taken out of it, not added on top.
What you type is what leaves the building: a server that permits 4000 kbit/s gets 4000.
The line underneath shows the split as you type: → video 3840 + audio 160 = 4000 kbit/s.
So raising the audio bitrate takes bitrate away from the picture. On a service with music, that trade is usually worth making; on speech, it is not.
Reasonable starting points
| Situation | Size | Total |
|---|---|---|
| Speech, modest upload | 1280 × 720 | 2500 kbit/s |
| General use | 1280 × 720 | 4000 kbit/s |
| Music, plenty of upload | 1920 × 1080 | 6000 kbit/s |
Set the total to what your upload can carry all the time, not to its peak. A stream that fits comfortably is worth more than one that is beautiful for twenty minutes and then falls apart.
The status block reports dropped frames — frames the network could not carry. If those appear, the bitrate is too high for the line, whatever the speed test says.