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AVCHD / MP4 playback differences on computer and TV


apoon204
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Hi all,

I am using Pana GX7 to shoot AVCHD/MP4 movie at 1080/50p@28Mbps. Long story short, if I playback the clip on computer (latest retina iMac with i7 and 24G RAM), it looks a little bit “jump” frame. It happens significantly when the video is panning. It just looks not smooth. Both VLC and Quicktime perform the same. I tried both AVCHD and MP4 format but no difference at all – same problem.

However, if I play the same file on my Panasonic Viera TV via USB (direct playback the MTS file), it is silky smooth on the screen, everything just perfect.

Has anyone have similar experience?

Question: is there some technical issue / differences behind the computer and TV on processing the video clip? Am I missing something on setting? Is it possible to render the video to be playback in computer like the quality in TV?

Many thanks for your advices!

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Thanks Inazuma.

So does it mean the video from GX7 is "not as smooth" as we thought?! You said "TV create frames", that mean the original 50p video is "not enough frame" to show the smoothness on screen? Would you mind explore more on that (as I am a newcomer in movie)?

Many many thanks.

Are there any opinions from other members? I'd like to take movie as best as it can as those are my kids memory... any thoughts to make the existing videos to playback in better quality?

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People watching videos with computers dont like to have smooth or realistic motion. Blurred or jerky motion is the "standard" of cinema production and computer monitors. Using a TV for real cinema experience is not recommended here. At least you must switch off every features that may improve motion resolution or smoothness. And many say that shooting 50P or 60P looks cheap and videoish.

Switch your graphics card/monitor to 50Hz and you get decent (but still blurred) motion with your GX7. TV does that automatically but improves motion resolution too (which is of course a bad thing).

Computer monitor can never show motion resolution better than 300 lines even with 4k. Still a cheap fullHD TV can show about 1000 lines of horizontal motion resolution. More info about sharp motion here:

http://***URL removed***/forums/post/52942296

 

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Thanks Inazuma.

So does it mean the video from GX7 is "not as smooth" as we thought?! You said "TV create frames", that mean the original 50p video is "not enough frame" to show the smoothness on screen? Would you mind explore more on that (as I am a newcomer in movie)?

Many many thanks.

Are there any opinions from other members? I'd like to take movie as best as it can as those are my kids memory... any thoughts to make the existing videos to playback in better quality?

No matter how smooth you record your video, it will still look smoother on your TV due to the feature I mentioned earlier. It's not that your camera is at fault, it's that your TV is doing extra work. Also you should note that almost all films are shown at 24fps; nowhere near the 50fps your camera is recording.

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People watching videos with computers dont like to have smooth or realistic motion. Blurred or jerky motion is the "standard" of cinema production and computer monitors. Using a TV for real cinema experience is not recommended here. At least you must switch off every features that may improve motion resolution or smoothness. And many say that shooting 50P or 60P looks cheap and videoish.

Switch your graphics card/monitor to 50Hz and you get decent (but still blurred) motion with your GX7. TV does that automatically but improves motion resolution too (which is of course a bad thing).

Computer monitor can never show motion resolution better than 300 lines even with 4k. Still a cheap fullHD TV can show about 1000 lines of horizontal motion resolution. More info about sharp motion here:

http://***URL removed***/forums/post/52942296

 

​Many thanks Vesku. I also read your replies in my similar thread at dpreview. Lots of discussion and knowledgeable information that I may take some time to go through and get back to you guys later. In fact I didn't expect there are lots of discussion about it (I thought no one will reply as I couldn't find any related discussion online before). Glad that I can hear from you :)

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No matter how smooth you record your video, it will still look smoother on your TV due to the feature I mentioned earlier. It's not that your camera is at fault, it's that your TV is doing extra work. Also you should note that almost all films are shown at 24fps; nowhere near the 50fps your camera is recording.

​Thanks Inazuma :)

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LCD or plasma? A plasma will show much smoother motion with its sub field motion than any computer monitor, which may be what you're seeing.

​Thanks TheRenaissanceMan.

My Panasonic Viera LCD TV is TH-L42ET5H.

I need to double check if there is any motion enhancement option turned on...

But my point is, I just wanna make sure the clip I recorded (1080, 50P, 28Mbps) from GX7 is problem-free. Those are the clips of my kids memory. Because as far as I know the 50P/60P should be smoother than 24P/25P in theory?

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LCD or plasma? A plasma will show much smoother motion with its sub field motion than any computer monitor, which may be what you're seeing.

​LCD or plasma TV will both show smooth motion. There is no "sub field motion" in plasma. It is a marketing term. There is just the same frame interpolation in both. TV shows sharp motion due to flickering backlight systems and it is smoothed or fluided with frame interpolation if needed. Computer monitor has none of these systems so the motion is very blurred and juddery.

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Since you mentioned you are a newcomer in movie i just ask an obvious question, when you shoot your AVCHD/MP4 movie at 1080/50p@28Mbps at what shutter do you have your cam? It should be no more than 1/100s for 50p, achieved by using nd filters so your aperture wont be skyhigh with that low shutter. On a sunny day your cam might choose a higher shutter in auto mode, maybe like 1/500s to compensate for the light. If you than pan your shot with a 1/500s shutter, that might look quite choppy on any screen that does not smoothen out video.

 

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Hi Celli,

Thanks for your idea. You right, I can never know what shutter speed it uses while filming in auto mode.

So as if you suggested the choppy look are due to the high shutter speed, is there any solution (in rendering/processing) to smoothen it in post-production?

Thanks.

 

 

Since you mentioned you are a newcomer in movie i just ask an obvious question, when you shoot your AVCHD/MP4 movie at 1080/50p@28Mbps at what shutter do you have your cam? It should be no more than 1/100s for 50p, achieved by using nd filters so your aperture wont be skyhigh with that low shutter. On a sunny day your cam might choose a higher shutter in auto mode, maybe like 1/500s to compensate for the light. If you than pan your shot with a 1/500s shutter, that might look quite choppy on any screen that does not smoothen out video.

 

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In 50P shutter speed is not so important. Background may look a little "strobo like" in fast pans but the pan and motion itself looks still quite smooth. There should not be any "jump frames". 

-Apoon204, have you tried computer/monitor in 50Hz? Is it possible in your system?

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No matter how smooth you record your video, it will still look smoother on your TV due to the feature I mentioned earlier. It's not that your camera is at fault, it's that your TV is doing extra work. Also you should note that almost all films are shown at 24fps; nowhere near the 50fps your camera is recording.

​Films look jerky on computer monitors as well, it isn't just video we shoot.

TV sets may do interpolation  if they have that feature and that will reduce stutter, but more importantly they will adjust the refresh to match the input. That is critical. A computer monitor does not do that, it will refresh at 60Hz no matter what your video frame rate was. So unless you shoot at 60p your video is going to stutter.

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​LCD or plasma TV will both show smooth motion. There is no "sub field motion" in plasma. It is a marketing term. There is just the same frame in both. TV shows sharp motion due to flickering backlight systems and it is smoothed or fluided with frame interpolation if needed. Computer monitor has none of these systems so the motion is very blurred and juddery.

You're right and you're wrong.  Sub field motion and 600hz are marketing, but plasma's motion rendering advantage over LCD is a well-known fact. Thus had to do with the fundamental differences in the ways the two technologies create images.

http://www.cnet.com/news/what-is-600hz/

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Vesku, I am now in office and will try to see if there is any setting about 50Hz in my iMac at home tonight.

In 50P shutter speed is not so important. Background may look a little "strobo like" in fast pans but the pan and motion itself looks still quite smooth. There should not be any "jump frames". 

-Apoon204, have you tried computer/monitor in 50Hz? Is it possible in your system?

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Hi Celli,

Thanks for your idea. You right, I can never know what shutter speed it uses while filming in auto mode.

Thanks.

 

​Look for the 'Flkr Decrease' option in the Motion Picture menus - that basically fixes the shutter speed to whatever you set it to (normally 1/100 second for 50p video i.e. '180 degree' shutter) when you shoot video in everything except iA, iA+, or Creative Video modes e.g. P, A, S, M modes on the top mode dial are fine. The only other way of doing it is to use Creative Video mode and select Shutter Priority (and set it to 1/100 again).

As others have said, if you do this, in very bright conditions you might need to use an ND (neutral density) filter on the front of the lens to stop the video being over-exposed because the camera can't reduce the lens aperture and ISO enough.

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