Due to an oversight, incoming footage frames were NOT converted to the
working pixel format (usually half or float). For most frames, this meant the
OCIO conversion would occur on frames while they were still in their source
format (usually either RGB8 or RGB16). This leads to rounding error
inaccuracies, but even worse GLSL will clamp integer textures to 1.0 potentially
losing a lot of data.
While later nodes would correctly convert to the appropriate format, by then it
would be too late. This commit corrects this issue, converting the frames to
float during the OCIO shader pass.
Several things are accomplished in this commit, including:
- Use OIIO instead of our own functions for pixel format conversions
(cleaner code/less for us to maintain)
- Fold all PixelService functions into the PixelFormat class
(cleaner code)
- Moved OpenGL pixel definitions to OpenGL classes and out of the
global classes.
- Add support for RGB buffers as well as RGBA (optimization)
Fixes a number of playback stuttering and general UI lag issues by setting all
background tasks to IdlePriority rather than LowPriority. While it was assumed
LowPriority tasks would always get scheduled below NormalPriority (e.g. main
thread) tasks, it turns out this is not always the case. If the background tasks
start consuming a lot of CPU cycles, the scheduler may use "dynamic scheduling"
to schedule them above the main thread regardless leading to UI lag. This is
apparently the case for all thread priorities apart from IdlePriority, which
is allegedly a special case where threads are *only* scheduled when other
threads aren't busy ensuring the main thread stays responsive.
context
More intuitive code flow and allows the user to undock the viewer (which
forcibly destroys and recreates the context) and the viewer will handle
creation of the new texture in said new context.
The workers run in separate threads meaning if any significant change is made
(e.g. parameters changing, or even closing the program), these workers may still
be mid-render. This is particularly problematic when closing since the nodes a
worker is rendering may be deleted mid-render. Render backends now have a
function that pauses the main thread (but starts a second event loop so the UI
isn't frozen) until the worker threads are all finished. This way, massive
changes can be made safely without race conditions.
We try to handle aspect ratios in metadata (e.g. stretching 1440x1080 videos
out to 1920x1080 when requested), and FFmpeg will usually return a 1/1
aspect ratio even if it can't determine an aspect ratio. However, as mentioned
in the documentation, sometimes it returns a 0/0 aspect ratio when it can't
determine an aspect ratio, which we didn't handle and would lead to the code
allocating a buffer with a 0px height. This commit handles both 1/1 and 0/0
aspect ratios in accordance with the FFmpeg documentation.
Reference: https://www.ffmpeg.org/doxygen/4.0/structAVFrame.html#a62f9c20541a83d37db7072126ff0060d
Implementation isn't perfect yet, viewer/renderer doesn't update yet when
the preference is changed so a sequence needs to be re-opened for the change to
take effect.
By using one thread per logical CPU thread, we seemed to completely saturate
the CPU which would kill the performance of the main/GUI thread (despite the
other threads being low priority). We now use half of the logical threads, which
still sees good CPU usage and minimal performance impact while allowing the
main thread to respond to user actions.
itsmattkc