Faster H.265/HEVC Video Encoding with Nvidia GTX960 GPU and ffmpeg

H.265 promises the same video quality as H.264 when using half the bitrate, so you may have thought about converting your H.264 videos to H.265/HEVC in order to reduce the space used by your videos. However, if you’ve ever tried to transcoding videos with tools such as HandBrake, you’ll know the process can be painfully slow, and a single movie may take several hours even with a machine with a power processor. However, there’s a better and fster solution thanks to hardware accelerated encoding available in some Intel and Nvidia graphics cards. For this purpose, GearBest sent me Maxsun MS-GTX960 graphics card, a second generation Maxwell GPU, that supports H.265 accelerated video encoding and promised up to 500 fps video encoding. So I’ve put the graphics card to the test in a computer running Ubuntu 14.04, and reports some of my findings here. Similar instructions can also be followed in Windows.

In order to leverage Nvidia Maxwell 2 GPU capabilities you’ll need to download and install Nvidia Video Codec SDK. The latest version (6.0.1) requires Nvidia Drivers 358.xx or greater, and my system had version 352.xx, so I followed some instructions to install the latest drivers in Ubuntu 14.04.

Upon restart I had the latest 358.16 drivers installed.

Somehow the fonts were very small right after installation as xorg.conf was missing, so I recreated with the command:

Then I adjust the font sizes further with Unity Tweak Tool.

The next step is to download and extract nvidia_video_sdk_6.0.1.zip into a working directory:

The instructions in the Readme simply tell you to go to Samples directory, and type make in order to build the samples, but I had to do a few more steps:

I also had to modify Samples/NvTranscoder/Makefile to replace := by += in front of LDFLAGS.

and finally I could successfully build the samples:

There are several samples in the SDK: NvEncoder, NvEncoderCudaInterop, NvEncoderD3DInterop, NvEncoderLowLatency, NvEncoderPerf, NvTranscoder, NvDecodeD3D9, and NvDecodeGL. For the purpose of this post I used NvTranscoder to convert H.264 video to H.265 using the GPU.

At first I had some issues with the error:

I followed a workaround provided on Blender, and it did not work at first, but after using NvTranscoder with sudo once, I could use the tool as a normal user thereafter.

Here’s the output to transcode a H.264 1080p video with High Quality preset.

The video lasts 2 minutes 43 seconds (4901 frames in total), and encoding was done in about 32 seconds meaning about 5 times faster than real-time, and at 156.5 fps on average.

I repeated the same test by with High Performance preset.

Decoding took around 24 seconds at 205 fps. It looked pretty good, but I tried the same test with HandBrake using H.265 with RF quality set to 25, and it took 4 minutes and 30 seconds to encode the video, or about 9 times slower than with the GPU. For reference, my computer is based on an AMD FX8350 octa-core processor clocked at 4.0 GHz.

But then I tried to play the video, and I could not find any tool to play them, and NvTranscode  appears to generate raw H.265 video data, so as I did not want to write my own little program, I found that ffmpeg also support nvenc, but just not by default, and you have to compile it yourself.

There are instructions to build ffmpeg with nvenc in Ubuntu 15.10, but they did not work on Ubuntu 14.04 so I mixed those with ffmpeg Ubuntu compilation guide to build it for my computer.

First we’ll need to install some dependencies and create a working directory:

You’ll also need to download and install/compile some extra packages depending on the codecs we want to enable. I’ll skip H.264 and H.265 since this will be handled by Nvidia GPU instead, and will enable AAC and MP3 audio encoders, VP8/VP9 and XviD video decoders and encoders, and libopus decoder and encoder as explained in the building guide:

Now I’ll download and extract ffmpeg snapshot (January 3, 2016) and copy the required NVENC 6.0 SDK header files into /usr/local/include:

Before configuring and building ffmpeg with nvenc enabled:

You can also optionally install it (which I did):

This will install it in $HOME/bin/ffmpeg. Now we can verify nvenc support for H.264 and H.265 is enabled:

Perfect. Time for a test with our 1080p H.264 video sample, and encoding at 2000 kbps.

It took 30 seconds, or about the same time as with NvTranscode, but this time I had a watchable video with audio, and I could not notice any visual quality degradation.

I repeated the test with a H.264 1080p movie lasting 1 hour 57 minutes 29 seconds. The movie H.264 stream was encoded at 2150 kbps, so to decrease the file size by half I encoded the movie at 1075 kbps (-b:v 1075k option). The encoding only took 13 minutes and 12 seconds, or about 9 times faster real-time at 218 fps.

I also checked some GPU details during the transcoding:

This shows for example that it does not maxes out the GPU power consumption (P2 mode: 33 Watts). My processor load was however a bit higher than expected, although not at 100% all the time as would have been the case for software video transcoding.

Beside saving time, transcoding videos with a GPU graphics should also reduce your electricity bill. How much exactly will depend on your video library size, electricity rate, and overall computer power consumption.

While the original file size was 2.0GB, the H.265 video was only 985 MB large, and video quality appeared to be very close to the one of the original video.

Finally, I transcoded a 4K H.264 video @ 30 fps (big_buck_bunny_4k_H264_30fps.mp4) at slightly less half bitrate (3500 kbps for H.265 vs 7480 kbps for H.264) and it took 6 minutes and 56 seconds to encode the 10 minutes 30 seconds video. While checking quality the main problem was my computer struggled to cope with the H.265 4K video when using Totem and VLC video players with lots of artifacts at times, and sound cuts, but the videos played just fine with ffplay and Kodi.

I’d like to thanks GearBest for providing Maxsun MS-GTX960 graphics card selling for $240.04 on their website.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.

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