Framerate detection uses decimals in base when shouldn't #87776

New Issue

Gerard Taulats Braos · 2021-04-24T11:18:05+02:00

2021-04-24 11:18:05 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: Intel(R) HD Graphics 4600 Intel 4.3.0 - Build 20.19.15.5058

Blender Version
Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-04-21 20:15, hash: 932b23782a
Worked: Never

Short description of error
When importing a video in the sequencer, if the video was in 30 fps, Blender detects it as 3 fps and base 0.1
The more extreme case happens when rendering with decimal base, that importing this clip sets the fps to 32767 and the base to 1092.233 (matches 30 fps).

Exact steps for others to reproduce the error

Open blender with the Video Editing preset (does the same from the default scene)
Set framerate to 30 and render a video (1 frame is enough)
Import the video placing it in the sequencer
Check "Custom" on the framerate and notice fps and base
Further exploration:
Change the presets of file format to any except default (with Matroska doesn't happen this).
Render a video with 3 fps and base 0.1
Import the video and check "custom"

Some notes:

I discovered this issue several months ago, but I paid no mind due to being apparently harmless. I noticed that if the base is not 1, some decoders fail to open the videos (in my case playing videos online in Drive).
With FFMPEG seems to do so when using multiples of 10 (20, 30, 60, 120, etc.)
When rendering with the AVI internal (AVI JPEG or AVI RAW), when importing the video the fps are set to 10 and the base to 0.333
There are many more odd behaviors involved with different combinations of fps and base.
The behavior seems to be different in 2.77 (the one first included the automatic feature) and 2.78, where for example a framerate of 30 is set as 6 fps and base 0.2. From 2.79 behaves the same the same way as explained.

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: Intel(R) HD Graphics 4600 Intel 4.3.0 - Build 20.19.15.5058 **Blender Version** Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-04-21 20:15, hash: `932b23782a` Worked: Never **Short description of error** When importing a video in the sequencer, if the video was in 30 fps, Blender detects it as 3 fps and base 0.1 The more extreme case happens when rendering with decimal base, that importing this clip sets the fps to 32767 and the base to 1092.233 (matches 30 fps). **Exact steps for others to reproduce the error** - Open blender with the Video Editing preset (does the same from the default scene) - Set framerate to 30 and render a video (1 frame is enough) - Import the video placing it in the sequencer - Check "Custom" on the framerate and notice fps and base Further exploration: - Change the presets of file format to any except default (with Matroska doesn't happen this). - Render a video with 3 fps and base 0.1 - Import the video and check "custom" Some notes: - I discovered this issue several months ago, but I paid no mind due to being apparently harmless. I noticed that if the base is not 1, some decoders fail to open the videos (in my case playing videos online in Drive). - With FFMPEG seems to do so when using multiples of 10 (20, 30, 60, 120, etc.) - When rendering with the AVI internal (AVI JPEG or AVI RAW), when importing the video the fps are set to 10 and the base to 0.333 - There are many more odd behaviors involved with different combinations of fps and base. - The behavior seems to be different in 2.77 (the one first included the automatic feature) and 2.78, where for example a framerate of 30 is set as 6 fps and base 0.2. From 2.79 behaves the same the same way as explained.

Gerard Taulats Braos commented

2021-04-24 11:18:05 +02:00

Added subscriber: @Tabra

Evan Wilson commented

2021-04-25 10:41:35 +02:00

Added subscriber: @EAW

Evan Wilson commented

2021-04-25 10:41:35 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Evan Wilson commented

2021-04-25 10:41:35 +02:00

I can reproduce using 3.0 master 87a70801c6.

FFmpeg wants the base to be an Integer.

https://github.com/FFmpeg/FFmpeg/blob/master/libavutil/rational.h

While rational numbers can be expressed as floating-point numbers, the
conversion process is a lossy one, so are floating-point operations. On the
other hand, the nature of FFmpeg demands highly accurate calculation of
timestamps. This set of rational number utilities serves as a generic
interface for manipulating rational numbers as pairs of numerators and
denominators.

Apparently this issue has come up before and was partially fixed in 956cb4f403

I can reproduce using 3.0 master 87a70801c6a9. ![FPS 3 Base 0.100.png](https://archive.blender.org/developer/F10037090/FPS_3_Base_0.100.png) FFmpeg wants the base to be an Integer. https://github.com/FFmpeg/FFmpeg/blob/master/libavutil/rational.h > While rational numbers can be expressed as floating-point numbers, the > conversion process is a lossy one, so are floating-point operations. On the > other hand, the nature of FFmpeg demands highly accurate calculation of > timestamps. This set of rational number utilities serves as a generic > interface for manipulating rational numbers as pairs of numerators and > denominators. Apparently this issue has come up before and was partially fixed in 956cb4f403

Sergey Sharybin commented

2021-05-03 15:19:44 +02:00

Added subscribers: @iss, @Sergey

Sergey Sharybin commented

2021-05-03 15:19:45 +02:00

@iss, Do you feel like you can look into the issue in a long term?

P.S. A long term is because this isn't a newly introduced problem, but it does feel like we do need to bring the fps and related topics under control.

@iss, Do you feel like you can look into the issue in a long term? P.S. A long term is because this isn't a newly introduced problem, but it does feel like we do need to bring the fps and related topics under control.

Richard Antalik commented

2021-05-04 01:37:36 +02:00

I should be able to have a look and find solution. I have noticed more places where FPS calculation fails or causes problems as well.

Philipp Oeser removed the

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Framerate detection uses decimals in base when shouldn't #87776