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4K Video Playback


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Show Sage ran two 4k mpeg4 movies from a single computer as part of our exhibit at LDI this year (last weekend).

The video was derived from a stock house 8k original and it was split and encoded into two 4k mpeg4 files by the stock house.

I need to check on the specific graphics card model, I know it was a newer Radeon series card with four outputs.

Computer was i7 six-core Extreme edition with SSD drive.

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I just bought an Analog Way Acsender 32 and it accept 4K input. It has DP plug at the back so probably I will use DP cable for it.

 

jfk or TomT, did you need any EDID management during the graphics card output set up ? Can you give us more information about the codecs, frame rates ?

 

A powerful CPU and SSD is easy to solve.

 

Thanks.

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Sedat, on 27 Nov 2013 - 06:49, said:

...

jfk or TomT, did you need any EDID management during the graphics card output set up ?

We did not, wish we had.

Our experience is worth mentioning. Ran for a three day show.

First day ran flawlessly.

Second day started out with with a repeating crash that at first was unidentifiable.

What clearly appeared to be a software issue was in fact a hardware issue,

specifically display signal chain.

BTW I don't take credit for identifying this issue, I am just the reporter in this case ;)

Our 4k monitors only accepted HDMI 1.4 for 4k signals.

From the monitor to the graphics card, our connection was

3940x2160@30p monitor 2m High Speed HDMI 1.4 cable HDMI 1.4 to MDP high speed active 4k adaptor graphics card

x2 monitors on the same Radeon graphics card.

And there was the rub.

Three non-locking connection points per monitor and gravity can have strange affects.

If a display connection was fully breaking, it would have been obvious. But in this case,

a marginal connection never lost signal to the display,

yet it would upset the graphics subsytem enough to tick off WATCHOUT

and send it into a non-recoverable state.

Seems watchdog was attemping to bring it back and failing, but don't hold me to that observation.

 

Very misleading to say the least.

Why would you suspect the cabling if the display never lost signal,

never blinked, flashed or exhibited any other behavior that would point at the connections?

But that is what it turned out to be.

Simply reconfirming all six connections (and adding strain relief to fight gravity)

eliminated the issue and the system ran fine for the day.

Next/last morning, same problem, same solution, same clean run for the day.

I suspect a solid EDID manager and care for the MDP connection would have masked

any anomalies farther down the signal chain.

 

Sedat, on 27 Nov 2013 - 06:49, said:

Can you give us more information about the codecs, frame rates ?

Not for the content run last Fri-Sat-Sun at this time, content was only rented for the show and was encoded by the stock house. (.m4v)

 

However, we have been testing with our current Extreme build with three different gpus -

ATi FirePro W7000 (4-output), ATi FireProW9000 (6-output) and the Radeon (4-output) we used at the show.

In the shop, were are testing mpeg4 videos that are encoded at different bit rates and frame rates.

Our test videos ...

  • Video 1,Bees: 4096x2304, 22.1Mbps, 24.00fps, MPEG4 (.m4v)
  • Video 2, New Zealand: 4096x2304, 19.1Mbps, 23.97fps, MPEG4 (.m4v)
  • Video 3, Landscape: 3840x2160, 17.2Mbps, 29.97fps, MPEG4 (.m4v)

We could play all three at the same time smoothly in our testing, albeit scaling the three down

into the two displays, as we don't have a third for testing at this time.

Sedat, on 27 Nov 2013 - 06:49, said:

A powerful CPU and SSD is easy to solve. Thanks.

Agreed, for 4k it is quite cost effective even if it is pushing the limits of PC $$.

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To. jfk

 

What was used cable? HDMI 1.4? DP?

 

Don't know how I missed that earlier, but the answer is in the post above.  ;)

 

What was in the MPEG4 files? H.264? I assume it would take a pretty hefty machine to play two 4k H.264. Framerate?

 

Mike

 

Gosh, missed that one two. Also covered in the post above  ;)

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  • 11 months later...

This is one I used:

 

ffmpeg -y -threads auto \

-i "/Volumes/rawvideo/R3D_3840x2160_30FPS.mp4" \
-f vob -vcodec mpeg2video -b:v 80000k -minrate 80000k -maxrate 80000k -g 15 -bf 2 -an -trellis 2 \
"/Users/mike/Desktop/3840x2160-80MBit.mpg" 
 
I also made some tests with H264, which also worked fine, although MPEG2 is less taxing on the CPU.
 
We recently ran three 4k outputs from a single chassis, which seemed to work well. This was on a fairly beefy AMD card, with DisplayPort straight to the displays (running 4k at 60Hz).
 
Mike
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Here's another similar example, this one encoding staight from an image sequence (which is often a more practical source format:

 

ffmpeg -y -threads auto \

-r 25 -i "/Volumes/Backup/InkDrop4kJpeg/InkDrop4kHD[0000-3827]%04d.jpg" \
-f vob -vcodec mpeg2video -b:v 60000k -minrate 60000k -maxrate 60000k -g 15 -bf 2 -an -trellis 2 \
"/Users/mike/Desktop/inkDrops-60MBit.mpg" 
 
Hope this helps.
 
Mike
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Hi Mike,

 

That's great, thank you! 60-80Mb/s gave satisfactory results in mpeg2? I've been testing with some downloaded 50Mb/s h264 files which look good; I wasn't sure how much higher the data rate might need to be for comparable quality in mpeg2. Anyway, thanks again for those commands - they will make a good starting point for testing.

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  • 1 year later...

I would recommend skipping the "-bf 2" option in ffmpeg, alternatively select an IPPP... gop structure (no B-frames) if using some other tool for encoding, for best playback performance. If encoding in constant quality, the bitrate gain from allowing B-frames is quite small (around 5%, but it depends somewhat on the kind of content), but the decoding process is a lot more complex, with the need to keep more reference frames in memory. If encoding using constant bitrate, it will be very hard (if at all possible) to tell the difference between the two (no B-frames or allow B-frames). If you're worried about the quality, just bump up the bitrate by 5-10%, this bitrate increase will have a much smaller impact on the performance than allowing B-frames.

 

/Erik 

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  • 1 year later...

 

This is one I used:

 

ffmpeg -y -threads auto \

-i "/Volumes/rawvideo/R3D_3840x2160_30FPS.mp4" \
-f vob -vcodec mpeg2video -b:v 80000k -minrate 80000k -maxrate 80000k -g 15 -bf 2 -an -trellis 2 \
"/Users/mike/Desktop/3840x2160-80MBit.mpg" 
 
I also made some tests with H264, which also worked fine, although MPEG2 is less taxing on the CPU.
 
We recently ran three 4k outputs from a single chassis, which seemed to work well. This was on a fairly beefy AMD card, with DisplayPort straight to the displays (running 4k at 60Hz).
 
Mike

 

Hi Mike,

 

I'm doing some tests converting 4K to MPEG2 using ffmpeg and doesn't work. When I try to compress 4096x2048 and 4096x1708 ffmpeg message me "width or high are not allowed to be multiples of 4096 add -strict -1 if you want to use them anyway". And if I add it then conversion works but can't the media compressed doesn't work.

 

This is the command line I use:

ffmpeg.exe -i "INPUT/%name%.mp4" -f vob -vcodec mpeg2video -strict -1 -b:v %bitrate% -minrate %bitrate% -maxrate %bitrate% -g 15 -bf 0 -an -trellis 2 "OUTPUT/%name%.mpg"

 

Any idea or advise?

 

Thanks

Quim

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