ffmpeg - Hardware Acceleration using GPU - Benchmark

Null muxer

A simple way to benchmark decoding is to use the null muxer:

ffmpeg -i input -f null -

NOTE: The following parts of the command forces a null file:

-f null -

Linux and macOS users can add the time command:

time ffmpeg -i input -f null -

returns:

[...]
real	0m3.115s
user	0m0.223s
sys	0m0.244s

NOTE: See man time for more info.

The -benchmark option can be added to output CPU time and maximum memory consumption:

time ffmpeg -i input -benchmark -f null -

returns:

[...]
bench: utime=0.154s stime=0.196s rtime=3.000s
bench: maxrss=365256kB

If you want to just decode a particular stream then use the map option:

ffmpeg -i input -map 0:a:0 -f null -

NOTE: Another approach to ignore streams is to use:

You can decode with one thread if you want to:

ffmpeg -threads 1 -i input -f null -

NOTE: Not all decoders have threading capabilities and some have several.

You can check decoder details such as

ffmpeg -h decoder=h264

There can be several decoders available for a format.

You can name the decoder if you do not want to rely on the default:

ffmpeg -c:v vp8 -i input -f null -
ffmpeg -c:v libvpx -i input -f null -

ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 -hwaccel_output_format vaapi -i input.mp4 -c:v hevc_vaapi -q:v 28 -f null - -benchmark

returns:

...
bench: utime=0.156s stime=0.195s rtime=3.003s
bench: maxrss=358944kB

NOTE: maxrss indicates the maximum RAM used during the ffmpeg execution.

utime: user time.
- utime is the sum of processing time across all threads. Since they may operate in parallel, utime can exceed rtime.
stime: system time.
rtime: real time.