Problem when rendering - rendered file is very "choppy" (frame rate seems lower than reality)

Hi,

Getting a weird problem with the frame rate/smoothness of a video I’ve just rendered using HitFIlm Express.

The rendered video is coming out very “choppy”; i.e. – it’s almost as if it’s only running @ 15 fps, or that it’s smooth, but occasionally frames are “dragging” (being shown for a touch too long, before going to the next one).

The source video is totally smooth, and has no issues. It’s only the rendered video that’s got the choppiness issues, and the rendered video is solely made of clips from the original source video.

Doesn’t seem to be any issues with the audio.

 

Some notes about the render;

  • Source video is 25 fps, rendered video is also 25 fps (used the Frame Rate: As Source) in the export options
  • Both videos are .mp4, 1080p files
  • Source video is a very long YouTube video (7+ hours), that I have downloaded & edited clips into a shorter version, to make the rendered video

So due to the source nature, I’m very limited in any tweaking I can do to the original source file

  • When I important the original source video into HitFilm Express, it took a couple hours to “conform audio”, before the file was ready for editing.

No idea if this could be causing the problem or not, but thought it was worth a mention

 

Any help?

 

PS – I’ve attached the information I’ve got from MediaInfo on both files below

 

MediaInfo - #1 Source Video

 

General

Format                                   : MPEG-4

Format profile                           : Base Media

Codec ID                                 : isom (isom/iso2/avc1/mp41)

File size                                : 7.99 GiB

Duration                                 : 7 h 31 min

Overall bit rate                         : 2 531 kb/s

Writing application                      : Lavf56.40.101

 

Video

ID                                       : 1

Format                                   : AVC

Format/Info                              : Advanced Video Codec

Format profile                           : [email protected]

Format settings                          : CABAC / 2 Ref Frames

Format settings, CABAC                   : Yes

Format settings, RefFrames               : 2 frames

Codec ID                                 : avc1

Codec ID/Info                            : Advanced Video Coding

Duration                                 : 7 h 31 min

Duration_FirstFrame                      : -40 ms

Bit rate                                 : 2 398 kb/s

Width                                    : 1 920 pixels

Height                                   : 1 080 pixels

Display aspect ratio                     : 16:9

Frame rate mode                          : Variable

Frame rate                               : 25.000 FPS

Minimum frame rate                       : 25.000 FPS

Maximum frame rate                       : 25.014 FPS

Color space                              : YUV

Chroma subsampling                       : 4:2:0

Bit depth                                : 8 bits

Scan type                                : Progressive

Bits/(Pixel*Frame)                       : 0.046

Stream size                              : 7.57 GiB (95%)

Color range                              : Limited

Color primaries                          : BT.709

Transfer characteristics                 : BT.709

Matrix coefficients                      : BT.709

 

Audio

ID                                       : 2

Format                                   : AAC

Format/Info                              : Advanced Audio Codec

Format profile                           : LC

Codec ID                                 : mp4a-40-2

Duration                                 : 7 h 31 min

Bit rate mode                            : Constant

Bit rate                                 : 126 kb/s

Channel(s)                               : 2 channels

Channel positions                        : Front: L R

Sampling rate                            : 44.1 kHz

Frame rate                               : 43.066 FPS (1024 SPF)

Compression mode                         : Lossy

Stream size                              : 406 MiB (5%)

Default                                  : Yes

Alternate group                          : 1

 

 

MediaInfo - #2 Rendered Video

 

General

Format                                   : MPEG-4

Format profile                           : Base Media / Version 2

Codec ID                                 : mp42 (isom/mp42)

File size                                : 342 MiB

Duration                                 : 15 min 16 s

Overall bit rate mode                    : Variable

Overall bit rate                         : 3 128 kb/s

Video

ID                                       : 2

Format                                   : AVC

Format/Info                              : Advanced Video Codec

Format profile                           : [email protected]

Format settings                          : CABAC / 3 Ref Frames

Format settings, CABAC                   : Yes

Format settings, RefFrames               : 3 frames

Format settings, GOP                     : M=3, N=33

Codec ID                                 : avc1

Codec ID/Info                            : Advanced Video Coding

Duration                                 : 15 min 16 s

Bit rate mode                            : Variable

Bit rate                                 : 3 000 kb/s

Width                                    : 1 920 pixels

Height                                   : 1 080 pixels

Display aspect ratio                     : 16:9

Frame rate mode                          : Constant

Frame rate                               : 25.000 FPS

Standard                                 : PAL

Color space                              : YUV

Chroma subsampling                       : 4:2:0

Bit depth                                : 8 bits

Scan type                                : Progressive

Bits/(Pixel*Frame)                       : 0.058

Stream size                              : 328 MiB (96%)

Language                                 : English

Color range                              : Limited

Color primaries                          : BT.709

Transfer characteristics                 : BT.709

Matrix coefficients                      : BT.709

 

Audio

ID                                       : 1

Format                                   : AAC

Format/Info                              : Advanced Audio Codec

Format profile                           : LC

Codec ID                                 : mp4a-40-2

Duration                                 : 15 min 16 s

Bit rate mode                            : Variable

Bit rate                                 : 125 kb/s

Maximum bit rate                         : 151 kb/s

Channel(s)                               : 2 channels

Channel positions                        : Front: L R

Sampling rate                            : 48.0 kHz

Frame rate                               : 46.875 FPS (1024 SPF)

Compression mode                         : Lossy

Stream size                              : 13.7 MiB (4%)

Language                                 : English

Comments

  • Triem23
    Triem23 Posts: 20,399 Power User

    Your source footage is variable frame rate and should be converted to a constant frame rate. 

    Ways to do this and why it matters here. 

    https://youtu.be/Yqhl0mRuTng

    Once transcoded, right click source files in the media bin, select Relink then choose the transcoded files. This will swap your original for your transcoded video. You'll need to review your edit to make certain nothing changed in the timing  but you'll keep most of your prior work intact. 

  • @Triem23 Thanks for the solution, did as you suggested and it's now worked, the new rendered video is now much less choppy than before. 

    It's crazy to think, what appears to be just a tiny variation of frame rate of 0.014 FPS, has caused a problem this large!

    For future reference, is there any way to get HitFilm to work with variable frame rates? Or allow it to export as a variable frame rate?

    Just wondering since it although it did work, it took many hours to transcode, re-comform the audio in HitFilm, then re-render the video, so this will become very tedious task if I need to do this for every video. (Is every YouTube video a variable frame rate?)

  • CleverTagline
    CleverTagline Posts: 3,345 Ambassador

    Transcoding before editing should become part of your workflow. Professional editors transcode, but we never see that in the behind-the-scenes glory shots of big projects being edited, so the assumption tends to be that we can dump any type of video into an editing program and it should "just work." Variable frame rate works best for playback, not editing, as the video by @Triem23 above explains, so expecting editing software to support it is a bit unrealistic. The fact that VFR media is even usable at all in HitFilm is a testament to the developers, but my gut says that the choppiness we see is about as good as we can realistically expect.

    I kind of see HitFilm like an animal. I could feed an animal just about anything, but if I want it to be truly healthy, it would be wise to take the time to learn about the types of food that are best for that animal, even if it costs more money and/or time. With HitFilm, I would much rather spend the extra time to transcode my media so that HitFilm runs smoothly, instead of dealing with sluggish interactivity and frequent crashes. (On the crashing front, HitFilm used to crash multiple times A DAY when I was just tossing any old footage into it. Since I was turned on to transcoding, it crashes maybe once or twice A YEAR.)

This discussion has been closed.