(VERY) wrong bitrate when encoding H264

[sharoni]

I have used WonderFox HD Video Converter Factory on Windows to compress the un-necessarily huge video files which phones and cameras produce, and resulting bit rates were very close to what I defined.

However, recently, H264 compression results in video data rates that are usually 2-10X larger than I define, different for each file in the batch, and without any apparent logic. Restarting the app does not change the results. I tried another leading app - Wondershare UniConverter, and had a similar problem - first few runs were OK, and then consistently wrong bitrates. When encoding H265 - results are correct bitrate in both apps. I tried 3 other recommended converters, which had other issues for me, so I never got to testing them beyond a few runs.

Could it be that there's a bug in some H264 encoder underlying both apps (and maybe this encoder was auto-updated and now has a bug)
How do I manage encoders which the conversion apps use?
And which encoder is recommended?

Or even better, can someone recommend a "good" video converter.. ?
- see my next post for what I'd like.

Thanks!

[davexnet]

Are you using 2-pass VBR for your bitrate control ?

[sharoni]

Are you using 2-pass VBR for your bitrate control ?

nope
in the apps I used VBR causes very big bitrates.
on most of them 2 pass is not offered.

[davexnet]

You're doing it wrong. Use 2-pass vbr and set the bitrate required specifically.
Thats what this mode is for - predictable bitrate, predictable file size.
Try Vidcoder/Handbrake

[sharoni]

You're doing it wrong. Use 2-pass vbr and set the bitrate required specifically.
Thats what this mode is for - predictable bitrate, predictable file size.
Try Vidcoder/Handbrake

Interesting, will try!
I always thought 2 pass was used only to enhance compression.
In any case, VBR may be a solution for my needs, but does not explain why CBR compressed properly, and then stopped.
Thanks!

[davexnet]

You're doing it wrong. Use 2-pass vbr and set the bitrate required specifically.
Thats what this mode is for - predictable bitrate, predictable file size.
Try Vidcoder/Handbrake

Interesting, will try!
I always thought 2 pass was used only to enhance compression.
In any case, VBR may be a solution for my needs, but does not explain why CBR compressed properly, and then stopped.
Thanks!

AVC (H.264) doesn't have a CBR mode

[jagabo]

AVC (H.264) doesn't have a CBR mode

x264 doesn't support CBR but some other h.264 encoders do. But basically, you should never use CBR.