QOpenGLWidget video rendering perfomance in multiple processes
My problem may seem vague without code, but it actually isn't.
So, there I've got an almost properly-working widget, which renders video frames.
Qt 5.10 and QOpenGLWidget subclassing worked fine, I didn't make any sophisticated optimizations -- there are two textures and a couple of shaders, converting YUV pixel format to RGB -- glTexImage2D() + shaders, no buffers.
Video frames are obtained from FFMPEG, it shows great performance due to hardware acceleration... when there is only one video window.
The piece of software is a "video wall" -- multiple independent video windows on the same screen. Of course, multi-threading would be the preferred solution, but legacy holds for now, I can't change it.
So, 1 window with Full HD video consumes ~2% CPU & 8-10% GPU regardless of the size of the window. But 7-10 similar windows, launched from the same executable at the same time consume almost all the CPU. My math says that 2 x 8 != 100...
My best guesses are:
- This is a ffmpeg decoder issue, hardware acceleration still is not magic, some hardware pipeline stalls
- 7-8-9 independent OpenGL contexts cost a lot more than 1 cost x N
- I'm not using PUBO or some other complex techniques to improve OpenGL rendering. It still explains nothing, but at least it is a guess
The behavior is the same on Ubuntu, where decoding uses different codec (I mean that using GPU accelerated or CPU accelerated codecs makes no difference!), so, it makes more probable that I'm missing something about OpenGL... or not, because launching 6-7 Qt examples with dynamic textures shows normal growth of CPU usages -- it is approximately a sum for the number of windows.
Anyway, it becomes quite tricky for me to profile the case, so I hope someone could have been solving the similar problem before and could share his experience with me. I'd be appreciated for any ideas, how to deal with the described riddle.
I can add any pieces of code if that helps.
c++ qt opengl ffmpeg
edited Nov 24 '18 at 18:13
marc_s
577k12911141259
asked Nov 23 '18 at 17:44
MasterAlerMasterAler
463512
|
show 2 more comments
My problem may seem vague without code, but it actually isn't.
So, there I've got an almost properly-working widget, which renders video frames.
Qt 5.10 and QOpenGLWidget subclassing worked fine, I didn't make any sophisticated optimizations -- there are two textures and a couple of shaders, converting YUV pixel format to RGB -- glTexImage2D() + shaders, no buffers.
Video frames are obtained from FFMPEG, it shows great performance due to hardware acceleration... when there is only one video window.
The piece of software is a "video wall" -- multiple independent video windows on the same screen. Of course, multi-threading would be the preferred solution, but legacy holds for now, I can't change it.
So, 1 window with Full HD video consumes ~2% CPU & 8-10% GPU regardless of the size of the window. But 7-10 similar windows, launched from the same executable at the same time consume almost all the CPU. My math says that 2 x 8 != 100...
My best guesses are:
- This is a ffmpeg decoder issue, hardware acceleration still is not magic, some hardware pipeline stalls
- 7-8-9 independent OpenGL contexts cost a lot more than 1 cost x N
- I'm not using PUBO or some other complex techniques to improve OpenGL rendering. It still explains nothing, but at least it is a guess
The behavior is the same on Ubuntu, where decoding uses different codec (I mean that using GPU accelerated or CPU accelerated codecs makes no difference!), so, it makes more probable that I'm missing something about OpenGL... or not, because launching 6-7 Qt examples with dynamic textures shows normal growth of CPU usages -- it is approximately a sum for the number of windows.
Anyway, it becomes quite tricky for me to profile the case, so I hope someone could have been solving the similar problem before and could share his experience with me. I'd be appreciated for any ideas, how to deal with the described riddle.
I can add any pieces of code if that helps.
c++ qt opengl ffmpeg
edited Nov 24 '18 at 18:13
marc_s
577k12911141259
asked Nov 23 '18 at 17:44
MasterAlerMasterAler
463512
If the issue is with CPU then you should profile your code. If you use old fixed-pipeline OpenGL then perhaps, only perhaps, you have an issue with RAM-to-GPU data movement. These are only guesses. Without profiling and seeing your code nothing can be asserted.
– Ripi2
Nov 23 '18 at 19:18
Qt's problem? Unsure. I don't want to mislead you but: software.intel.com/en-us/articles/… How is that applicable to your problem exactly, I wish I could express it in the actual answer.
– Alexander V
Nov 24 '18 at 5:03
1
I roughly remember that OpenGL context switches are expensive. However, I remember also thatQOpenGLWidgets may share a context. There's a subject in Qt doc. for this: Context Sharing
– Scheff
Nov 24 '18 at 11:20
@Ripi2, good guess but no, I'm using shaders/buffers and all other stuff from the new pipeline.It has to be profiling, but the tricky thing is somewhat about I described: one "demo.exe" works fine, eight exe's simultaneously work lame. And they share no data at all =(
– MasterAler
Nov 26 '18 at 12:32
@AlexanderV, yeah, that's about OpenGL optimizations, was thinking to use some of it, but my doubt origins in single-launched-app good perfomance. I'd consder it to be the bottleneck otherwise.
– MasterAler
Nov 26 '18 at 12:33
|
show 2 more comments
My problem may seem vague without code, but it actually isn't.
So, there I've got an almost properly-working widget, which renders video frames.
Qt 5.10 and QOpenGLWidget subclassing worked fine, I didn't make any sophisticated optimizations -- there are two textures and a couple of shaders, converting YUV pixel format to RGB -- glTexImage2D() + shaders, no buffers.
Video frames are obtained from FFMPEG, it shows great performance due to hardware acceleration... when there is only one video window.
The piece of software is a "video wall" -- multiple independent video windows on the same screen. Of course, multi-threading would be the preferred solution, but legacy holds for now, I can't change it.
So, 1 window with Full HD video consumes ~2% CPU & 8-10% GPU regardless of the size of the window. But 7-10 similar windows, launched from the same executable at the same time consume almost all the CPU. My math says that 2 x 8 != 100...
My best guesses are:
- This is a ffmpeg decoder issue, hardware acceleration still is not magic, some hardware pipeline stalls
- 7-8-9 independent OpenGL contexts cost a lot more than 1 cost x N
- I'm not using PUBO or some other complex techniques to improve OpenGL rendering. It still explains nothing, but at least it is a guess
The behavior is the same on Ubuntu, where decoding uses different codec (I mean that using GPU accelerated or CPU accelerated codecs makes no difference!), so, it makes more probable that I'm missing something about OpenGL... or not, because launching 6-7 Qt examples with dynamic textures shows normal growth of CPU usages -- it is approximately a sum for the number of windows.
Anyway, it becomes quite tricky for me to profile the case, so I hope someone could have been solving the similar problem before and could share his experience with me. I'd be appreciated for any ideas, how to deal with the described riddle.
I can add any pieces of code if that helps.
c++ qt opengl ffmpeg
edited Nov 24 '18 at 18:13
marc_s
577k12911141259
asked Nov 23 '18 at 17:44
MasterAlerMasterAler
463512
My problem may seem vague without code, but it actually isn't.
So, there I've got an almost properly-working widget, which renders video frames.
Qt 5.10 and QOpenGLWidget subclassing worked fine, I didn't make any sophisticated optimizations -- there are two textures and a couple of shaders, converting YUV pixel format to RGB -- glTexImage2D() + shaders, no buffers.
Video frames are obtained from FFMPEG, it shows great performance due to hardware acceleration... when there is only one video window.
The piece of software is a "video wall" -- multiple independent video windows on the same screen. Of course, multi-threading would be the preferred solution, but legacy holds for now, I can't change it.
So, 1 window with Full HD video consumes ~2% CPU & 8-10% GPU regardless of the size of the window. But 7-10 similar windows, launched from the same executable at the same time consume almost all the CPU. My math says that 2 x 8 != 100...
My best guesses are:
- This is a ffmpeg decoder issue, hardware acceleration still is not magic, some hardware pipeline stalls
- 7-8-9 independent OpenGL contexts cost a lot more than 1 cost x N
- I'm not using PUBO or some other complex techniques to improve OpenGL rendering. It still explains nothing, but at least it is a guess
The behavior is the same on Ubuntu, where decoding uses different codec (I mean that using GPU accelerated or CPU accelerated codecs makes no difference!), so, it makes more probable that I'm missing something about OpenGL... or not, because launching 6-7 Qt examples with dynamic textures shows normal growth of CPU usages -- it is approximately a sum for the number of windows.
Anyway, it becomes quite tricky for me to profile the case, so I hope someone could have been solving the similar problem before and could share his experience with me. I'd be appreciated for any ideas, how to deal with the described riddle.
I can add any pieces of code if that helps.
c++ qt opengl ffmpeg
c++ qt opengl ffmpeg
edited Nov 24 '18 at 18:13
marc_s
577k12911141259
asked Nov 23 '18 at 17:44
MasterAlerMasterAler
463512
edited Nov 24 '18 at 18:13
marc_s
577k12911141259
asked Nov 23 '18 at 17:44
MasterAlerMasterAler
463512
edited Nov 24 '18 at 18:13
marc_s
577k12911141259
edited Nov 24 '18 at 18:13
marc_s
577k12911141259
edited Nov 24 '18 at 18:13
marc_s
577k12911141259
577k12911141259
asked Nov 23 '18 at 17:44
MasterAlerMasterAler
463512
asked Nov 23 '18 at 17:44
MasterAlerMasterAler
463512
asked Nov 23 '18 at 17:44
MasterAlerMasterAler
463512
463512
If the issue is with CPU then you should profile your code. If you use old fixed-pipeline OpenGL then perhaps, only perhaps, you have an issue with RAM-to-GPU data movement. These are only guesses. Without profiling and seeing your code nothing can be asserted.
– Ripi2
Nov 23 '18 at 19:18
Qt's problem? Unsure. I don't want to mislead you but: software.intel.com/en-us/articles/… How is that applicable to your problem exactly, I wish I could express it in the actual answer.
– Alexander V
Nov 24 '18 at 5:03
1
I roughly remember that OpenGL context switches are expensive. However, I remember also thatQOpenGLWidgets may share a context. There's a subject in Qt doc. for this: Context Sharing
– Scheff
Nov 24 '18 at 11:20
@Ripi2, good guess but no, I'm using shaders/buffers and all other stuff from the new pipeline.It has to be profiling, but the tricky thing is somewhat about I described: one "demo.exe" works fine, eight exe's simultaneously work lame. And they share no data at all =(
– MasterAler
Nov 26 '18 at 12:32
@AlexanderV, yeah, that's about OpenGL optimizations, was thinking to use some of it, but my doubt origins in single-launched-app good perfomance. I'd consder it to be the bottleneck otherwise.
– MasterAler
Nov 26 '18 at 12:33
|
show 2 more comments
If the issue is with CPU then you should profile your code. If you use old fixed-pipeline OpenGL then perhaps, only perhaps, you have an issue with RAM-to-GPU data movement. These are only guesses. Without profiling and seeing your code nothing can be asserted.
– Ripi2
Nov 23 '18 at 19:18
Qt's problem? Unsure. I don't want to mislead you but: software.intel.com/en-us/articles/… How is that applicable to your problem exactly, I wish I could express it in the actual answer.
– Alexander V
Nov 24 '18 at 5:03
1
I roughly remember that OpenGL context switches are expensive. However, I remember also thatQOpenGLWidgets may share a context. There's a subject in Qt doc. for this: Context Sharing
– Scheff
Nov 24 '18 at 11:20
@Ripi2, good guess but no, I'm using shaders/buffers and all other stuff from the new pipeline.It has to be profiling, but the tricky thing is somewhat about I described: one "demo.exe" works fine, eight exe's simultaneously work lame. And they share no data at all =(
– MasterAler
Nov 26 '18 at 12:32
@AlexanderV, yeah, that's about OpenGL optimizations, was thinking to use some of it, but my doubt origins in single-launched-app good perfomance. I'd consder it to be the bottleneck otherwise.
– MasterAler
Nov 26 '18 at 12:33
If the issue is with CPU then you should profile your code. If you use old fixed-pipeline OpenGL then perhaps, only perhaps, you have an issue with RAM-to-GPU data movement. These are only guesses. Without profiling and seeing your code nothing can be asserted.
– Ripi2
Nov 23 '18 at 19:18
If the issue is with CPU then you should profile your code. If you use old fixed-pipeline OpenGL then perhaps, only perhaps, you have an issue with RAM-to-GPU data movement. These are only guesses. Without profiling and seeing your code nothing can be asserted.
– Ripi2
Nov 23 '18 at 19:18
Qt's problem? Unsure. I don't want to mislead you but: software.intel.com/en-us/articles/… How is that applicable to your problem exactly, I wish I could express it in the actual answer.
– Alexander V
Nov 24 '18 at 5:03
Qt's problem? Unsure. I don't want to mislead you but: software.intel.com/en-us/articles/… How is that applicable to your problem exactly, I wish I could express it in the actual answer.
– Alexander V
Nov 24 '18 at 5:03
1
1
I roughly remember that OpenGL context switches are expensive. However, I remember also that
QOpenGLWidgets may share a context. There's a subject in Qt doc. for this: Context Sharing– Scheff
Nov 24 '18 at 11:20
I roughly remember that OpenGL context switches are expensive. However, I remember also that
QOpenGLWidgets may share a context. There's a subject in Qt doc. for this: Context Sharing– Scheff
Nov 24 '18 at 11:20
@Ripi2, good guess but no, I'm using shaders/buffers and all other stuff from the new pipeline.It has to be profiling, but the tricky thing is somewhat about I described: one "demo.exe" works fine, eight exe's simultaneously work lame. And they share no data at all =(
– MasterAler
Nov 26 '18 at 12:32
@Ripi2, good guess but no, I'm using shaders/buffers and all other stuff from the new pipeline.It has to be profiling, but the tricky thing is somewhat about I described: one "demo.exe" works fine, eight exe's simultaneously work lame. And they share no data at all =(
– MasterAler
Nov 26 '18 at 12:32
@AlexanderV, yeah, that's about OpenGL optimizations, was thinking to use some of it, but my doubt origins in single-launched-app good perfomance. I'd consder it to be the bottleneck otherwise.
– MasterAler
Nov 26 '18 at 12:33
@AlexanderV, yeah, that's about OpenGL optimizations, was thinking to use some of it, but my doubt origins in single-launched-app good perfomance. I'd consder it to be the bottleneck otherwise.
– MasterAler
Nov 26 '18 at 12:33
|
show 2 more comments
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If the issue is with CPU then you should profile your code. If you use old fixed-pipeline OpenGL then perhaps, only perhaps, you have an issue with RAM-to-GPU data movement. These are only guesses. Without profiling and seeing your code nothing can be asserted.
– Ripi2
Nov 23 '18 at 19:18
Qt's problem? Unsure. I don't want to mislead you but: software.intel.com/en-us/articles/… How is that applicable to your problem exactly, I wish I could express it in the actual answer.
– Alexander V
Nov 24 '18 at 5:03
1
I roughly remember that OpenGL context switches are expensive. However, I remember also that
QOpenGLWidgets may share a context. There's a subject in Qt doc. for this: Context Sharing– Scheff
Nov 24 '18 at 11:20
@Ripi2, good guess but no, I'm using shaders/buffers and all other stuff from the new pipeline.It has to be profiling, but the tricky thing is somewhat about I described: one "demo.exe" works fine, eight exe's simultaneously work lame. And they share no data at all =(
– MasterAler
Nov 26 '18 at 12:32
@AlexanderV, yeah, that's about OpenGL optimizations, was thinking to use some of it, but my doubt origins in single-launched-app good perfomance. I'd consder it to be the bottleneck otherwise.
– MasterAler
Nov 26 '18 at 12:33