Play multiple videos in one subplot

2018 1 9
2 个回答
回答已采纳
更新时间：2018 1 10
1 次查看（30 天）

0 个投票

Hi,
I'm trying to play multiple avi videos in one subplot, and borrowed online code but always showing me the following error:
Error using VideoReader/read (line 134)
Cannot call READ method after using READFRAME or HASFRAME methods or setting the CURRENTTIME property. Recreate the object to read a frame at a
specific frame index.
Error in videoplay (line 18)
v1frame = v1.read(i1);
And here is the code:
clc;clear all;
v1= VideoReader('\\cab-fs07.mae.virginia.edu\NewData\NHTSA\2016-AutomatedVehicle\1Simulation\Project\RESULTV3.5\M50-OS_Standard_Reclined_0_Int_0_RMDB\1_cut.avi');
v1.CurrentTime = 1.5;
v1_numFrames = ceil(v1.FrameRate*v1.Duration);
v2= VideoReader('\\cab-fs07.mae.virginia.edu\NewData\NHTSA\2016-AutomatedVehicle\1Simulation\Project\RESULTV3.5\M50-OS_Standard_Reclined_0_Int_0_RMDB\2_top.avi');
v2.CurrentTime = 1.5;
v2_numFrames = ceil(v2.FrameRate*v2.Duration);
i1 = 0;
i2 = 0;
fig = gcf;
ax1 = subplot(2,2,1, 'Parent', fig);
ax2 = subplot(2,2,2, 'Parent', fig);
currAxes = axes;
while i1 < v1_numFrames && i2 < v2_numFrames
if i1 < v1_numFrames
i1 = i1+1;
v1frame = v1.read(i1);
if isempty(v1frame) %unexpected!
warning(sprintf('skipped v1 empty frame #%d', i1));
elseif ishandle(ax1)
image(v1frame, 'Parent', ax1);
else
break; %axes is gone, figure is probably gone too
end
end
if i2 < v2_numFrames
i2 = i2+1;
v2frame = v2.read(i2);
if isempty(v2frame) %unexpected!
warning(sprintf('skipped v2 empty frame #%d', i2));
elseif ishandle(ax2)
image(v2frame, 'Parent', ax2);
end
end
drawnow
end
Thanks

请先登录，再回答此问题。

 采纳的回答

Walter Roberson
Walter Roberson 2018-1-9

0 个投票

You use v1.read(i1) after v1.CurrentTime = 1.5 . You can only use read() if you have never set the CurrentTime. You will need to switch to readFrame()
Warning: multiplying framerate by duration has round-off error even for fixed framerates, and is just plain wrong for variable frame rates. The only way to accurately know the number of frames is to loop reading frames and counting them.
I recommend that you do not bother to try to estimate frames and instead use a structure like
while true
got_one = false;
had_problem = false;
if hasFrame(v1)
v1frame = readFrame(v1);
if isvalid(ax1)
image(v1frame, 'Parent', ax1);
got_one = true;
else
had_problem = true;
end
end
if had_problem; break; end
if hasFrame(v2)
v2frame = readFrame(v2);
if isvalid(ax2)
image(v2frame, 'Parent', ax2);
got_one = true;
else
had_problem = true;
end
end
if had_problem; break; end
if ~got_one; break; end
drawnow();
end
Except that I would recommend changing the CData of the image objects instead of using image() calls, for performance reasons.

4 个评论
显示 2更早的评论 隐藏 2更早的评论

Hongnan Lin
Hongnan Lin 2018-1-9
Thanks Walter! It's really helpful. However, I have another problem which is if I don't Ctrl+C, the code will never stop running and were displayed. Is there any way to solve it? Thanks!
Walter Roberson
Walter Roberson 2018-1-9
The got_one logic is designed to end as soon as both objects run out of frames. Could you do a bit of debugging to see which of the two objects is thinking it has remaining frames? The code I posted should end as soon as the longer video ends.
Hongnan Lin
Hongnan Lin 2018-1-10
Thanks for the reply Walter. Actually the videos I want to play are of the same frame numbers.
Walter Roberson
Walter Roberson 2018-1-10
When you use the debugger, is hasFrame(v1) or hasFrame(v1) returning true?

请先登录，再进行评论。

更多回答（1 个）

Hongnan Lin
Hongnan Lin 2018-1-10
编辑：Walter Roberson 2018-1-10

0 个投票

Thanks Walter!
Here is another problem:
As attached is the figure to show, I'd rather hide all the axis however, there are only axis in the last plot hidden.
Following is the code:
while true
thisFrame = getframe(gcf);
i1 = i1+1
got_one = false ;
had_problem = false ;
if hasFrame(v1)
v1frame = readFrame(v1);
if isvalid(ax1)
image(v1frame, 'Parent', ax1);
axis off;
got_one = true ;
else
had_problem = true ;
end
end
if had_problem;
break;
end
if hasFrame(v2)
v2frame = readFrame(v2);
if isvalid(ax2)
image(v2frame, 'Parent', ax2);
axis off;
got_one = true ;
else
had_problem = true ;
end
end
if had_problem;
break;
end;
if ~got_one;
break;
end
image(v3,'Parent', ax3);%for .png
axis off;
% set(gcf,'PaperUnits','inches','Position',[1 1 1500 400]);
writeVideo(v, thisFrame);
Thanks
Lin

1 个评论
显示 -1更早的评论 隐藏 -1更早的评论

Walter Roberson
Walter Roberson 2018-1-10
编辑：Walter Roberson 2018-1-10
axis(ax1, 'off');
and
axis(ax2, 'off');
and
axis(ax3, 'off')
Note: it is more efficient to update the CData property of an existing image than to image() and axis()

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Convert Image Type 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by