what to expect?

(click here for two html embedded test video files, if the user’s browser can playback 264x and 265x)

while x264 and x265 are surely great codecs, the re-encoding of x264 to x265 is very CPU and thus time and energy intense and on preset  -crf 28 + mp3 audio (for material of high importance aac would be prefered) should yield at least reduction by -30% in file size.

SOMETIMES even Google’s webp format (VP9 codec) might have a BIGGER FILESIZE than the x264 mp4 version of the same content.

resolutions SD (480p) vs Full HD (1080p) vs 4K Ultra HD vs 8K Ultra HD (click to view original size)

example: AMD Ryzen 5 5900G using all 6 cores manages to re-encode 1920×1080 (Full HD) with only 18fps, which depending on the source material (30fps) is half the speed of playback, so the user can imagine how slow things become with 4k and 8k re-encoding 😀

So in order to judge if it’s worth re-encoding a lot of material, really depends on:


cat /etc/os-release; # tested on
PRETTY_NAME="Debian GNU/Linux 11 (bullseye)"

apt install ffmpeg

ffmpeg --version
ffmpeg version 4.3.5-0+deb11u1 Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 10 (Debian 10.2.1-6)


# keep the resolution, simply reencode with x265 (2x smaller)
ffmpeg -i "input.mp4" -vcodec libx265 -crf 28 output.mp4

# reencode with x265 and reduce the resolution by 50% (file size 4.4x smaller)
ffmpeg -i "input.mp4" -vcodec libx265 -crf 28 -vf "scale=trunc(iw/4)*2:trunc(ih/4)*2" output.mp4

# more examples
# maximum compression (warning! very cpu intensive!)
f=filename.mp4;nice -n 19 ffmpeg -threads 2 -i "$f" -vcodec libx265 -crf 28 -preset slow -c:a mp3 "$f".soft.x265.mp4

# high compression + better aac sound (still pretty cpu intensive!)
f=filename.mp4;nice -n 19 ffmpeg -threads 2 -i "$f" -vcodec libx265 -crf 28 -preset medium -c:a aac "$f".soft.x265..mp4

hardware encoding?

according to src it should be possible 😀

test if hardware accelerated encoding/decoding is available/possible:

hostnamectl ; # tested with
  Operating System: Debian GNU/Linux 11 (bullseye)
            Kernel: Linux 5.10.0-21-amd64
      Architecture: x86-64

cat /proc/cpuinfo |head
processor	: 0
vendor_id	: AuthenticAMD
cpu family	: 25
model		: 80
model name	: AMD Ryzen 5 5600G with Radeon Graphics
stepping	: 0
microcode	: 0xa50000d
cpu MHz		: 4116.583
cache size	: 512 KB

su - root; # install
apt update
apt install vainfo
vainfo; # run it 
libva info: VA-API version 1.10.0
libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/radeonsi_drv_video.so
libva info: Found init function __vaDriverInit_1_10
libva info: va_openDriver() returns 0
vainfo: VA-API version: 1.10 (libva 2.10.0)
vainfo: Driver version: Mesa Gallium driver 20.3.5 for AMD RENOIR (DRM 3.40.0, 5.10.0-21-amd64, LLVM 11.0.1)
vainfo: Supported profile and entrypoints
      VAProfileMPEG2Simple            :	VAEntrypointVLD
      VAProfileMPEG2Main              :	VAEntrypointVLD
      VAProfileVC1Simple              :	VAEntrypointVLD
      VAProfileVC1Main                :	VAEntrypointVLD
      VAProfileVC1Advanced            :	VAEntrypointVLD
      VAProfileH264ConstrainedBaseline:	VAEntrypointVLD
      VAProfileH264ConstrainedBaseline:	VAEntrypointEncSlice
      VAProfileH264Main               :	VAEntrypointVLD
      VAProfileH264Main               :	VAEntrypointEncSlice
      VAProfileH264High               :	VAEntrypointVLD
      VAProfileH264High               :	VAEntrypointEncSlice
      VAProfileHEVCMain               :	VAEntrypointVLD
      VAProfileHEVCMain               :	VAEntrypointEncSlice
      VAProfileHEVCMain10             :	VAEntrypointVLD
      VAProfileHEVCMain10             :	VAEntrypointEncSlice
      VAProfileJPEGBaseline           :	VAEntrypointVLD
      VAProfileVP9Profile0            :	VAEntrypointVLD
      VAProfileVP9Profile2            :	VAEntrypointVLD
      VAProfileNone                   :	VAEntrypointVideoProc

# what hwacc is supported?
ffmpeg -hide_banner -hwaccels
Hardware acceleration methods:

ffmpeg -h encoder=hevc_vaapi -hide_banner
Encoder hevc_vaapi [H.265/HEVC (VAAPI)]:
    General capabilities: delay hardware 
    Threading capabilities: none
    Supported hardware devices: vaapi 
    Supported pixel formats: vaapi_vld
h265_vaapi AVOptions:
  -low_power             E..V...... Use low-power encoding mode (only available on some platforms; may not support all encoding features) (default false)
  -idr_interval              E..V...... Distance (in I-frames) between IDR frames (from 0 to INT_MAX) (default 0)
  -b_depth                   E..V...... Maximum B-frame reference depth (from 1 to INT_MAX) (default 1)
  -rc_mode                   E..V...... Set rate control mode (from 0 to 6) (default auto)
     auto            0            E..V...... Choose mode automatically based on other parameters
     CQP             1            E..V...... Constant-quality
     CBR             2            E..V...... Constant-bitrate
     VBR             3            E..V...... Variable-bitrate
     ICQ             4            E..V...... Intelligent constant-quality
     QVBR            5            E..V...... Quality-defined variable-bitrate
     AVBR            6            E..V...... Average variable-bitrate
  -qp                        E..V...... Constant QP (for P-frames; scaled by qfactor/qoffset for I/B) (from 0 to 52) (default 0)
  -aud                   E..V...... Include AUD (default false)
  -profile                   E..V...... Set profile (general_profile_idc) (from -99 to 255) (default -99)
     main            1            E..V......
     main10          2            E..V......
     rext            4            E..V......
  -tier                      E..V...... Set tier (general_tier_flag) (from 0 to 1) (default main)
     main            0            E..V......
     high            1            E..V......
  -level                     E..V...... Set level (general_level_idc) (from -99 to 255) (default -99)
     1               30           E..V......
     2               60           E..V......
     2.1             63           E..V......
     3               90           E..V......
     3.1             93           E..V......
     4               120          E..V......
     4.1             123          E..V......
     5               150          E..V......
     5.1             153          E..V......
     5.2             156          E..V......
     6               180          E..V......
     6.1             183          E..V......
     6.2             186          E..V......
  -sei                     E..V...... Set SEI to include (default hdr)
     hdr                          E..V...... Include HDR metadata for mastering display colour volume and content light level information

# hardware encoding works! :D
# + CPU around ~10% (power usage down 90%)
# + encoding performance is up to 6x playback or 162 fps, which is great :D
# o reduction in filesize depends on the bitrate
# a -50% reduction for a 1920x1080 with 25fps was acchieved with 1220k bitrate
# without losing too much details and getting too much compression artifacts (pixely squares)
# - problem: user MUST SET bitrate MANUALLY (-b:v 2M = 2MBit/s, -b:v 1220k/s ...)
ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 -hwaccel_output_format vaapi -i "$f" -c:v hevc_vaapi -rc_mode 3 -b:v 1220k "$f.hard.x265.mp4"

script it:

  • this will re-encode all *.mp4 in the current directory
  • video encoding/decoding it a very CPU & energy intense process (if not hardware accelerated)
    • example: depending on resolution of video:
      • AMD-Ryzen-5600G re-encodes x264 to x265 at 1.5x the speed of playback (or ~40fps) while using 125W!
vim /scripts/reencode_x265.sh

echo "=== re encoding all video.mp4 files in the current directory via ffmpeg and x265 ==="
for f in *.mp4 ; do 
   time ffmpeg -i "$f" -vcodec libx265 -crf 28 "$f".x265.recompressed.mp4

To scale to half size:

vim /scripts/reencode_x265_half_size.sh

echo "=== re encoding all video.mp4 in the current directory via ffmpeg and x265 plus reducing resolution by HALF! ==="
# for $FILENAME in ./*.mp4; do
for f in *.mp4 ; do
time ffmpeg -i "$f" -vcodec libx265 -crf 28 "$f".x265.recompressed.mp4
   time ffmpeg -i "$f" -vf "scale=trunc(iw/4)*2:trunc(ih/4)*2" -c:v libx265 -crf 28 "$f".half-size.x265.mp4

more examples:

ffmpeg -i input.mkv -vf "scale=trunc(iw/4)*2:trunc(ih/4)*2" -c:v libx265 -crf 28 half_the_frame_size.mkv

One third size:

ffmpeg -i input.mkv -vf "scale=trunc(iw/6)*2:trunc(ih/6)*2" -c:v libx265 -crf 28 a_third_the_frame_size.mkv

One quarter size:

ffmpeg -i input.mkv -vf "scale=trunc(iw/8)*2:trunc(ih/8)*2" -c:v libx265 -crf 28 a_fourth_the_frame_size.mkv

One fifth size:

ffmpeg -i input.mkv -vf "scale=trunc(iw/10)*2:trunc(ih/10)*2" -c:v libx265 -crf 28 a_fifth_the_frame_size.mkv

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