Brief bitrate drops when using "Constant Bitrate"

Sethos

Hey,

Ever since HitFilm 3 was released, I've been dealing with this problem.

When I take any sort of footage, run it through HitFilm and want to render it using Constant Bitrate in 60FPS, regardless of the other settings, I see massive bitrate drops during playback. Like it plays back beautifully and suddenly the footage goes completely dithered for a split-second, then back to the normal quality.

I need to use Variable Bitrate to avoid it, however Variable seems to have some of the same tendencies albeit much, much less visible. 

Here's an example. Granted it's a fairly poor example but gives you an idea what I'm talking about; http://www.gfycat.com/ShrillWelcomeGalapagoshawk - Obviously this is heavily compressed due to being a .webm, however what I'd like to point out is the sudden massive dither / blur that happens a few seconds in, twice in a row. That is VERY pronounced when viewing it back in 1080p at a 100k+ bitrate. 

And it happens every single time, despite of the original source, whether it's a game recording fresh off ShadowPlay, something rendered pre-hand in Sony Vegas or otherwise. As long as I use Constant Bitrate, it happens.

 

PC:

Windows 8.1

5960x @ 4.4GHz

2 x Asus 980 

16GB DDR4

NullUnit

I have also had this happen to me. So, far it seems (for me) that this really only happens if I use a compressed mp4 file as my source footage. For instance, I wanted to do a quick color grade on a clip I took with my samsung galaxy. The format it records in is, of course, compressed mp4. I didn't feel like converting it to an editing format so I imported it directly into HF3 and got pretty much the exact type of rendering issues I see in your clip and they would happen in the same place every time. Same with when I needed to help a friend with a quick edit and all they had were compressed mp4s. 

So, I was able to "fix" the problem by taking the time to converting the mp4s into DNxHD (a proper editing format) and the renders looked fine after that. I wonder if the screen capture software that your using is recording in mp4 or a similar compressed format?

Here is a thread with more details about good file formats for HF.

http://hitfilm.com/forum/discussion/6132/stupid-technology-questions#latest

Sethos

Hey,

Appreciate the reply.

My primary source of footage is indeed .mp4 as I'm working on video game machinimas primarily. ShadowPlay, Nvidia's recording software outputs in .mp4 exclusively and when I render / re-render anything in Vegas Pro 13, I use MainConcept AVC/AAC which also outputs in .mp4. 

So it's very likely that it's the problem.

However, I have no real option of changing the output format. Would you have any recommendations for a (Free?) decent piece of converting software I could use as a bandaid fix for now?

In the long run however, it would be great if the issue was sorted as I sometime work with tons of .mp4 file recordings, having to convert everything would just get tedious in the long run.

I like to export / render with HitFilm, as Vegas' 60FPS renderings have caused some headaches in the past for me.