Next click the Encoder Config button.
Audio Send Ahead: Used to assist with video sound
synchronization problems
Min/Max Frame Sync: set for 0/120
Audio Format: AAC Plus or Lame (MP3) – AAC Plus offers the best compression rate
for audio.
AAC Plus Encoder Options: All the pre-made encoder configurations are based on 24 kbps Mono.
Video: VP62/VFW – All the pre-made encoder configurations are based upon
VP6.2 and are the best.
You can view additional information about
audio encoding here.
Now click the Configure Button:
| Using the pre-made encoder configurations, click on the settings tab and pick one of the pre-made configurations for the desired output bit rate and FPS you want. Be sure you always match up the set FPS with the selection or the rate will be off. |
|
Click OK and go back to the main NSVCAP screen.
You are now ready to encode.
Click ‘Start Capture’ when ready. |
 |
Technical Details: The pre-made configurations range from 80 kbps @ 20 fps, to 200 kbps @ 30 fps. As 30 fps is the highest fps rate used, it was chosen as the starting point for adjustments. 24 kbps mono audio was used in all settings.
Given a 100 kbps target, 80 kbps was the target for video information. That combined with 24 kbps of audio results in 104 kbps total – the figure the configuration is designed to peak out at. This is the same for all configuration rates @ 30 fps – in that the video target is
approximately 20k below the desired output.
When dealing with 20 fps for the same output
rate, the primary adjustment made was to the video target bitrate and was increased to bring the output rate up to match the desired output. Since 10 fps of information are missing, the video quality specifically was used to fill the gap. Thus 20 fps configurations look better than their 30 fps counterparts as the video quality was increased to make up the difference.
Specific adjustments to the VP6 codec started from the following chart:
|
Bitrate |
size |
fps |
Max Btw Keys |
Quantizer |
Temporal |
Spatial |
Peak Bitrate |
Buffer |
|
|
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
|
30 |
320x240 |
15 |
600 |
12/56 |
20 |
40/60 |
95 |
5/5/5 |
|
|
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
|
40 |
160x120 |
15 |
600 |
12/56 |
20 |
40/60 |
85 |
5/5/5 |
|
|
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
|
80 |
320x240 |
20 |
500 |
11/54 |
20 |
37/55 |
90 |
5/5/6 |
|
|
- |
- |
- |
- |
- |
-- |
- |
- |
- |
|
|
100 |
320x240 |
30 |
450 |
10/52 |
20 |
35/50 |
95 |
5/5/6 |
|
|
- |
- |
- |
- |
- |
-- |
- |
- |
- |
|
|
150 |
320x240 |
30 |
350 |
9/50 |
20 |
32/45 |
95 |
5/6/6 |
|
|
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
|
250 |
320x240 |
24-30 |
300 |
8/48 |
20 |
30/40 |
100 |
6/6/6 |
|
|
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
|
300 |
320x240 |
30 |
255 |
7/46 |
20 |
29/39 |
100 |
6/6/6 |
|
|
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
|
500 |
" |
30 |
210 |
6/44 |
20 |
25/37 |
100-125 |
6/6/6 |
|
|
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
|
750 |
" |
30 |
165 |
5/42 |
20 |
22/36 |
100-125 |
6/6/6 |
|
|
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
|
1000 |
480x368 |
24-30 |
120 |
4/40 |
20 |
20/35 |
100-150 |
6/6/6 |
|
The rows in italic
are taken directly from the On2 Technologies documentation.
From these general guidelines, and my own experiments,
I filled in some values in between these examples.
Using this as a guideline, I experimented with various
rates and compression.
|
