FFmpeg Quality Metrics

Calculate various video quality metrics with FFmpeg.

Currently supports:

• ✅ PSNR
• ✅ SSIM
• ✅ VIF
• ✅ MSAD
• ✅ VMAF

It will output:

• the per-frame metrics
• global statistics (min/max/average/standard deviation)
• a GUI, if you want to visualize the results interactively in a browser

Author: Werner Robitza [email protected]

Note

Previous versions installed a ffmpeg_quality_metrics executable. To harmonize it with other tools, now the executable is called ffmpeg-quality-metrics. Please ensure you remove the old executable (e.g. run which ffmpeg_quality_metrics and remove the file).

Contents:

• Requirements
• Usage
  • Metrics
  • Extended Options
• Examples
• Running with Docker
• Output
  • JSON Output
  • CSV Output
• GUI Visualization
  • Installation
  • Interactive Dashboard
• API
• Contributors
• License

---

Requirements

What you need:

• OS: Linux, macOS, Windows
• Python 3.9 or higher
• FFmpeg 7.1 or higher:
  • Linux: Download a build matching your platform from here.
  • macOS: Download the snapshot build from here or install via brew install ffmpeg.
  • Windows: Download an FFmpeg binary from here. The git essentials build will suffice.

Put the ffmpeg executable in your $PATH, e.g. /usr/local/bin/ffmpeg.

If you want to calculate VMAF, your ffmpeg build should include libvmaf. You also need the VMAF model files, which we bundle with this package, or you can download them from the VMAF GitHub.

Using uv:

uvx ffmpeg-quality-metrics

Using pipx:

pipx install ffmpeg-quality-metrics

Or, using pip:

pip3 install --user ffmpeg-quality-metrics

Usage

In the simplest case, if you have a distorted (encoded, maybe scaled) version and the reference:

ffmpeg-quality-metrics distorted.mp4 reference.y4m

The distorted file will be automatically scaled to the resolution of the reference, and the default metrics (PSNR, SSIM) will be computed.

Note that if your distorted file is not in time sync with the reference, you can use the --dist-delay option to delay the distorted file by a certain amount of seconds (positive or negative).

Note

Raw YUV files cannot be read with this tool. We should all be using lossless containers like Y4M or FFV1. If you have a raw YUV file, you can use FFmpeg to convert it to a format that this tool can read. Adjust the options as needed.

ffmpeg -framerate 24 -video_size 1920x1080 -pix_fmt yuv420p -i input.yuv output.y4m

Metrics

The following metrics are available in this tool:

Metric	Description	Scale	Components/Submetrics	Calculated by default?
PSNR	Peak Signal to Noise Ratio	dB (higher is better)	mse_avg mse_y mse_u mse_v psnr_avg psnr_y psnr_u psnr_v	✔️
SSIM	Structural Similarity	0-100 (higher is better)	ssim_y ssim_u ssim_v ssim_avg	✔️
VMAF	Video Multi-Method Assessment Fusion	0-100 (higher is better)	vmaf integer_adm2 integer_adm_scale0 integer_adm_scale1 integer_adm_scale2 integer_adm_scale3 integer_motion2 integer_motion integer_vif_scale0 integer_vif_scale1 integer_vif_scale2 integer_vif_scale3	No
VIF	Visual Information Fidelity	0-100 (higher is better)	scale_0 scale_1 scale_2 scale_3	No
MSAD	Mean Sum of Absolute Differences	depends on input video, minimum is 0 (higher is worse)	msad_y msad_u msad_v msad_avg	No

As shown in the table, every metric can have more than one submetric computed, and they will be printed in the output.

If you want to calculate additional metrics, enable them with the --metrics option:

ffmpeg-quality-metrics distorted.mp4 reference.avi --metrics psnr ssim vmaf

Specify multiple metrics by separating them with a space (e.g., in the above example, psnr ssim vmaf).

Here, VMAF uses the default model. You can specify a different model with the --vmaf-model option. VMAF also allows you to calculate even more additional features as submetrics. You can enable these with the --vmaf-features option.

Extended Options

You can configure additional options related to scaling, speed etc.

See ffmpeg-quality-metrics -h:

usage: ffmpeg-quality-metrics [-h] [-n] [-v] [-p] [-k] [--tmp-dir TMP_DIR]
                              [-m {vmaf,psnr,ssim,vif,msad} [{vmaf,psnr,ssim,vif,msad} ...]]
                              [-s {fast_bilinear,bilinear,bicubic,experimental,neighbor,area,bicublin,gauss,sinc,lanczos,spline}]
                              [-r FRAMERATE] [--dist-delay DIST_DELAY] [-t THREADS]
                              [--num-frames NUM_FRAMES] [--start-offset START_OFFSET]
                              [-o OUTPUT_FILE] [-of {json,csv}]
                              [--vmaf-model-path VMAF_MODEL_PATH]
                              [--vmaf-model-params VMAF_MODEL_PARAMS [VMAF_MODEL_PARAMS ...]]
                              [--vmaf-threads VMAF_THREADS] [--vmaf-subsample VMAF_SUBSAMPLE]
                              [--vmaf-features VMAF_FEATURES [VMAF_FEATURES ...]]
                              dist ref

ffmpeg-quality-metrics v3.4.2

positional arguments:
  dist                                  input file, distorted
  ref                                   input file, reference

options:
  -h, --help                            show this help message and exit

General options:
  -n, --dry-run                         Do not run commands, just show what would be done (default:
                                        False)
  -v, --verbose                         Show verbose output (default: False)
  -p, --progress                        Show a progress bar (default: False)
  -k, --keep-tmp                        Keep temporary files for debugging purposes (default: False)
  --tmp-dir TMP_DIR                     Directory to store temporary files in (will use system
                                        default if not specified) (default: None)

Metric options:
  -m {vmaf,psnr,ssim,vif,msad} [{vmaf,psnr,ssim,vif,msad} ...], --metrics {vmaf,psnr,ssim,vif,msad} [{vmaf,psnr,ssim,vif,msad} ...]
                                        Metrics to calculate. Specify multiple metrics like '--
                                        metrics ssim vmaf' (default: ['psnr', 'ssim'])

FFmpeg options:
  -s {fast_bilinear,bilinear,bicubic,experimental,neighbor,area,bicublin,gauss,sinc,lanczos,spline}, --scaling-algorithm {fast_bilinear,bilinear,bicubic,experimental,neighbor,area,bicublin,gauss,sinc,lanczos,spline}
                                        Scaling algorithm for ffmpeg (default: bicubic)
  -r FRAMERATE, --framerate FRAMERATE   Force an input framerate (default: None)
  --dist-delay DIST_DELAY               Delay the distorted video against the reference by this many
                                        seconds (default: 0.0)
  -t THREADS, --threads THREADS         Number of threads to do the calculations (default: 0)
  --num-frames NUM_FRAMES               Number of frames to analyze from the input files (default: all
                                        frames)
  --start-offset START_OFFSET           Seek to this position before analyzing. Accepts timestamp (e.g.,
                                        '00:00:10' or '10.5') or frame number with 'f:' prefix (e.g.,
                                        'f:100'). Note: seeking may not be frame-accurate due to keyframe
                                        constraints. (default: None)

Output options:
  -o OUTPUT_FILE, --output-file OUTPUT_FILE
                                        Output file for the metrics. If not specified, stdout will
                                        be used. (default: None)
  -of {json,csv}, --output-format {json,csv}
                                        Output format for the metrics (default: json)

VMAF options:
  --vmaf-model-path VMAF_MODEL_PATH     Use a specific VMAF model file. If none is chosen, picks a
                                        default model. You can also specify one of the following
                                        built-in models: ['vmaf_v0.6.1.json', 'vmaf_4k_v0.6.1.json',
                                        'vmaf_v0.6.1neg.json'] (default: /opt/homebrew/opt/libvmaf/s
                                        hare/libvmaf/model/vmaf_v0.6.1.json)
  --vmaf-model-params VMAF_MODEL_PARAMS [VMAF_MODEL_PARAMS ...]
                                        A list of params to pass to the VMAF model, specified as
                                        key=value. Specify multiple params like '--vmaf-model-params
                                        enable_transform=true enable_conf_interval=true' (default:
                                        None)
  --vmaf-threads VMAF_THREADS           Set the value of libvmaf's n_threads option. This determines
                                        the number of threads that are used for VMAF calculation.
                                        Set to 0 for auto. (default: 0)
  --vmaf-subsample VMAF_SUBSAMPLE       Set the value of libvmaf's n_subsample option. This is the
                                        subsampling interval, so set to 1 for default behavior.
                                        (default: 1)
  --vmaf-features VMAF_FEATURES [VMAF_FEATURES ...]
                                        A list of feature to enable. Pass the names of the features
                                        and any optional params. See https://github.com/Netflix/vmaf
                                        /blob/master/resource/doc/features.md for a list of
                                        available features. Params must be specified as 'key=value'.
                                        Multiple params must be separated by ':'. Specify multiple
                                        features like '--vmaf-features cambi:full_ref=true ciede'
                                        (default: None)

Seeking and Frame Selection

You can control which portion of the input videos to analyze using the --start-offset and --num-frames options.

To analyze only a specific number of frames (e.g., for faster processing or testing), use the --num-frames option:

ffmpeg-quality-metrics distorted.mp4 reference.y4m --num-frames 100

To skip the beginning of the video and start analysis at a specific position, use the --start-offset option. This accepts either a timestamp or a frame number:

# Seek to 10 seconds
ffmpeg-quality-metrics distorted.mp4 reference.y4m --start-offset 10

# Or use HH:MM:SS format
ffmpeg-quality-metrics distorted.mp4 reference.y4m --start-offset 00:00:10

# Seek to frame 100 (prefix with "f:")
ffmpeg-quality-metrics distorted.mp4 reference.y4m --start-offset f:100

> [!IMPORTANT]
> **Seeking Accuracy**: When using `--start-offset`, seeking may not be frame-accurate due to keyframe constraints in the video encoding. FFmpeg seeks to the nearest keyframe before the specified position and then decodes from there. For frame-accurate seeking, choose inputs that are all-I-frames like Y4M or FFV1.

### VMAF-specific Settings

As VMAF is more complex than the other metrics, it has a few more options.

#### Specifying VMAF Model

Use the `--vmaf-model-path` option to set the path to a different VMAF model file. The default is `vmaf_v0.6.1.json`.

`libvmaf` version 2.x supports JSON-based model files only. This program has built-in support for the following models:

vmaf_v0.6.1.json vmaf_4k_v0.6.1.json vmaf_v0.6.1neg.json

Use the `4k` version if you have a 4K reference sample. The `neg` version [is explained here](https://netflixtechblog.com/toward-a-better-quality-metric-for-the-video-community-7ed94e752a30).

You can either specify an absolute path to an existing model, e.g.:

/usr/local/opt/libvmaf/share/model/vmaf_v0.6.1neg.json

Or pass the file name to the built-in model. So all of these work:

```bash
# use a downloaded JSON model for libvmaf 2.x
ffmpeg-quality-metrics dist.mkv ref.mkv -m vmaf --vmaf-model-path vmaf_v0.6.1neg.json

# use a different path for models on your system
ffmpeg-quality-metrics dist.mkv ref.mkv -m vmaf --vmaf-model-path /usr/local/opt/libvmaf/share/model/vmaf_v0.6.1neg.json

Specifying VMAF Features

VMAF includes several metrics, each of which correspond to a feature name. By default, only three core features are used. Use the --vmaf-features option to enable additional features on top of the core features.

The following table shows the available features:

Metric	Feature name	Core feature in VMAF?
PSNR	psnr
PSNR-HVS	psnr_hvs
CIEDE2000	ciede
CAMBI	cambi
VIF	vif	✔️
ADM	adm	✔️
Motion	motion	✔️
SSIM	float_ssim
MS-SSIM	float_ms_ssim

To find out more about the features, check out the VMAF documentation.

For example, to enable the CAMBI feature, use:

ffmpeg-quality-metrics dist.mkv ref.mkv -m vmaf --vmaf-features cambi

To enable more than one feature, separate them with a space:

ffmpeg-quality-metrics dist.mkv ref.mkv -m vmaf --vmaf-features cambi psnr

VMAF Feature Parameters

Some features additionally take a number of optional parameters. The following table shows the available parameters for each feature:

Feature	Parameter	Default	Description
adm	adm_csf_mode	0	Contrast sensitivity function
adm	adm_enhn_gain_limit	100.0	Enhancement gain imposed on adm, must be >= 1.0, where 1.0 means the gain is completely disabled
adm	adm_norm_view_dist	3.0	Normalized viewing distance = viewing distance / ref display's physical height
adm	adm_ref_display_height	1080	Reference display height in pixels
adm	debug	false	Debug mode: enable additional output
cambi	enc_bitdepth		Encoding bitdepth.
cambi	enc_height		Encoding height.
cambi	enc_width		Encoding width.
cambi	eotf	bt1886	Determines the EOTF used to compute the visibility thresholds.
cambi	full_ref	false	Set to true to enable full-reference CAMBI calculation.
cambi	heatmaps_path		Set to a target folder where the CAMBI heatmaps will be stored as .gray files
cambi	max_log_contrast	2	Maximum contrast in log luma level (2^max_log_contrast) at 10-bits.
cambi	src_height		Source height. Only used when full_ref=true.
cambi	src_width		Source width. Only used when full_ref=true.
cambi	topk	0.2	Ratio of pixels for the spatial pooling computation.
cambi	tvi_threshold	0.75	Visibility threshold for luminance ΔL < tvi_threshold*L_mean.
cambi	window_size	63	Window size to compute CAMBI: 63 corresponds to ~1 degree at 4k.
motion	debug	true	Enable additional output for debugging.
motion	motion_force_zero	false	Force the motion score to be zero. This parameter is a feature-specific parameter.
ms_ssim	clip_db	false	Clip dB scores
ms_ssim	enable_db	false	Write MS-SSIM values as dB
ms_ssim	enable_lcs	false	Enable luminance, contrast and structure intermediate output
ssim	clip_db	false	Clip dB scores
ssim	enable_db	false	Write SSIM values as dB
ssim	enable_lcs	false	Enable luminance, contrast and structure intermediate output
vif	debug	false	Debug mode: enable additional output
vif	vif_enhn_gain_limit	100.0	Enhancement gain imposed on vif, must be >= 1.0, where 1.0 means the gain is completely disabled
vif	vif_kernelscale	1.0	Scaling factor for the gaussian kernel (2.0 means multiplying the standard deviation by 2 and enlarge the kernel size accordingly)

The parameters are specified as key=value pairs, separated by :. For example, to enable the full-reference CAMBI calculation, use:

ffmpeg-quality-metrics dist.mkv ref.mkv -m vmaf --vmaf-features cambi:full_ref=true

To generate the CAMBI heatmaps, use:

ffmpeg-quality-metrics dist.mkv ref.mkv -m vmaf --vmaf-features cambi:heatmaps_path=/tmp/cambi

VMAF Model Parameters

These parameters control the VMAF model itself (not the features).

Parameter	Description	Default
enable_transform	Enable the transform feature, which transforms the scores to represent quality as perceived on a phone (used to be called phone_model)	false
enable_conf_interval	Enable the confidence interval calculation	false

To specify these parameters, use the --vmaf-model-params option, and separate each parameter with a space. For example:

ffmpeg-quality-metrics dist.mkv ref.mkv -m vmaf --vmaf-model-params enable_transform=true enable_conf_interval=true

Note

The enable_conf_interval parameter currently does not change the output.

Examples

Run PSNR, SSIM, VMAF and VIF at the same time:

ffmpeg-quality-metrics dist.mkv ref.mkv \
    -m psnr ssim vmaf vif

Run VMAF with all the features:

ffmpeg-quality-metrics dist.mkv ref.mkv \
    -m vmaf \
    --vmaf-features ciede cambi psnr psnr_hvs motion adm vif

Enable feature options for CAMBI full-reference calculation:

ffmpeg-quality-metrics dist.mkv ref.mkv \
    -m vmaf \
    --vmaf-features cambi:full_ref=true

Running with Docker

You can use the pre-built image from Docker Hub:

docker run -v "$(pwd):/videos" -it slhck/ffmpeg-quality-metrics

Alternatively, download this repository and run

docker build -t ffmpeg-quality-metrics .

You can then run the container, which basically calls the Python script. To help you with mounting the volumes (since your videos are not stored in the container), you can run a helper script:

./docker_run.sh <dist> <ref> [OPTIONS]

Check the output of ./docker_run.sh for more help.

For example, to run the tool with the bundled test videos and enable VMAF calculation:

./docker_run.sh test/dist-854x480.mkv test/ref-1280x720.mkv -m vmaf

Output

This tool supports JSON or CSV output, including individual fields for planes/components/submetrics, and global statistics, as well as frame numbers (n). By default, the output is written to stdout. If you want to write the output to a file, use the -o/--output-file option:

ffmpeg-quality-metrics dist.mkv ref.mkv -m psnr -o output.json

The output file will be in the same format as the JSON output.

JSON Output

The JSON output will include a key for each metric, and the value will be a list of values for each frame. Each frame is a dictionary with individual metrics per frame.

For instance, PSNR and SSIM output averages as well as per-component metrics. VMAF outputs different metrics depending on the enabled features.

The global key contains global statistics for each metric and its submetrics.

See the example.json file for an example of the output.

CSV Output

CSV output is using the tidy data principle, using one column per feature and one line per frame (observation).

Example:

n,adm2,motion2,ms_ssim,psnr,ssim,vif_scale0,vif_scale1,vif_scale2,vif_scale3,vmaf,mse_avg,mse_u,mse_v,mse_y,psnr_avg,psnr_u,psnr_v,psnr_y,ssim_avg,ssim_u,ssim_v,ssim_y,input_file_dist,input_file_ref
1,0.70704,0.0,0.89698,18.58731,0.92415,0.53962,0.71805,0.75205,0.77367,15.44212,536.71,234.48,475.43,900.22,20.83,24.43,21.36,18.59,0.945,0.96,0.942,0.934,test/dist-854x480.mkv,test/ref-1280x720.mkv
2,0.7064,0.35975,0.89806,18.60299,0.9247,0.54025,0.71961,0.75369,0.77607,15.85038,535.29,239.4,469.49,896.98,20.84,24.34,21.41,18.6,0.946,0.96,0.943,0.934,test/dist-854x480.mkv,test/ref-1280x720.mkv
3,0.70505,0.35975,0.89879,18.6131,0.92466,0.5391,0.71869,0.75344,0.77616,15.63546,535.04,245.8,464.43,894.89,20.85,24.22,21.46,18.61,0.945,0.959,0.943,0.934,test/dist-854x480.mkv,test/ref-1280x720.mkv

As there is no tidy way to represent global data in the same CSV file, you can use other tools to aggregate the data.

GUI Visualization

This tool includes an optional interactive dashboard powered by Plotly Dash for visualizing quality metrics in the browser.

Installation

To use the GUI features, you need to install the optional gui dependencies.

Using uvx (recommended, no installation needed), you can run it directly:

# Run with GUI after calculation
uvx 'ffmpeg-quality-metrics[gui]' ffmpeg-quality-metrics dist.mp4 ref.mp4 --gui

# Or use the standalone viewer
uvx --from 'ffmpeg-quality-metrics[gui]' ffmpeg-quality-metrics-gui output.json

Or, if you've already installed the package as a local dependency, add the GUI extra dependencies:

# With uv
uv add 'ffmpeg-quality-metrics[gui]'

# Or with pip
pip install 'ffmpeg-quality-metrics[gui]'

Interactive Dashboard

After calculating metrics, you can launch an interactive dashboard with the --gui flag:

ffmpeg-quality-metrics dist.mp4 ref.mp4 --gui

This will:

1. Calculate the quality metrics as usual
2. Save the output (if --output-file is specified, otherwise will be kept in memory)
3. Open an interactive dashboard in your browser at http://127.0.0.1:8050

You can customize the host and port if needed:

ffmpeg-quality-metrics dist.mp4 ref.mp4 --gui --gui-host 0.0.0.0 --gui-port 8080

The dashboard includes:

• separate line charts for each primary metric (PSNR, SSIM, VMAF) with appropriate scales
• per-component breakdowns (Y/U/V planes, VIF scales)
• metric distributions
• statistics tables
• sortable table with all per-frame data

You can also visualize previously saved metrics files using the standalone viewer:

ffmpeg-quality-metrics-gui output.json

The GUI viewer supports loading multiple metrics files for side-by-side comparison:

ffmpeg-quality-metrics-gui file1.json file2.json file3.json

When multiple clips are loaded, the dashboard provides a distinct color for each clip.

API

The program exposes an API that you can use yourself:

from ffmpeg_quality_metrics import FfmpegQualityMetrics

ffqm = FfmpegQualityMetrics("path/to/reference-video.mp4", "path/to/distorted-video.mp4")

metrics = ffqm.calculate(["ssim", "psnr"])

# check the available metrics
print(metrics.keys())
# ['ssim', 'psnr']

# get the SSIM values for the first frame
print(metrics["ssim"][0])
# {'n': 1, 'ssim_y': 0.934, 'ssim_u': 0.96, 'ssim_v': 0.942, 'ssim_avg': 0.945}

# average the ssim_y values over all frames
print(sum([frame["ssim_y"] for frame in metrics["ssim"]]) / len(metrics["ssim"]))

# or just get the global stats
print(ffqm.get_global_stats()["ssim"]["ssim_y"]["average"])

For more usage please read the docs.

Contributors

Orkun Koçyiğit 💻	Hamas Shafiq 💻	Chris Griffith 💻	Ignacio Peletier 💻	Nav 🐛	Alexey Slobodiskiy 💻	ls-milkyway 💻
Anton Kesy 📖

License

ffmpeg-quality-metrics, Copyright (c) 2019-2025 Werner Robitza

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For VMAF models, see ffmpeg_quality_metrics/vmaf_models/LICENSE.