# vmaf

VMAF (Video Multi-Method Assessment Fusion) is a perceptual video quality assessment algorithm developed by Netflix. It combines multiple elementary quality metrics (VIF, DLM, Motion, ADM) and fuses them using a machine learning model to predict the perceived video quality as experienced by human viewers. VMAF scores range from 0 to 100, where higher scores indicate better perceptual quality.

This element is useful for:

- Evaluating video encoding quality and compression efficiency
- Comparing different encoding settings or codecs
- Quality assurance in video processing pipelines
- A/B testing of video content

For more information about VMAF, see: https://github.com/Netflix/vmaf

VMAF will perform perceptive video quality analysis on a set of input pads, the first pad is the reference video, the second is the distorted pad.

The image output will be the be the reference video pad, ref_pad.

VMAF will post a message containing a structure named "VMAF" at EOS or every reference frame if the property for frame-message=true.

The VMAF message structure contains the following fields:

- "timestamp" G_TYPE_UINT64 Buffer timestamp in nanoseconds
- "stream-time" G_TYPE_UINT64 Stream time in nanoseconds
- "running-time" G_TYPE_UINT64 Running time in nanoseconds
- "duration" G_TYPE_UINT64 Duration in nanoseconds
- "score" G_TYPE_DOUBLE The VMAF quality score (0-100, higher is better)
- "type" G_TYPE_STRING Message type: "frame" = per-frame score, "pooled" = aggregate score
- "index" G_TYPE_INT Frame index (only present for type="frame", per-frame messages)
- "psnr-y" G_TYPE_DOUBLE Peak Signal-to-Noise Ratio for Y (luma) channel in dB (only present if psnr property is enabled)
- "ssim" G_TYPE_DOUBLE Structural Similarity Index (0-1, higher is better) (only present if ssim property is enabled)
- "ms-ssim" G_TYPE_DOUBLE Multi-Scale Structural Similarity Index (0-1, higher is better) (only present if ms-ssim property is enabled)

The "type" field indicates whether the message contains a score for an individual frame (type="frame") or a pooled score for the entire stream up to that point (type="pooled"). Pooled scores are calculated at EOS using the pool-method property (mean, min, max, or harmonic mean).

The timing fields (timestamp, stream-time, running-time, duration) allow correlation of VMAF scores with specific video frames in the pipeline.

Per-frame messages (type="frame") include an "index" field indicating the frame number. With sub-sampling enabled, scores are only computed for frames at the sub-sampling rate, except motion scores which are computed for every frame.

It is possible to configure and run PSNR, SSIM, MS-SSIM together with VMAF by setting the appropriate properties to true.

For example, if ms-ssim, ssim, psnr are set to true, the emitted structure will look like this:

VMAF, timestamp=(guint64)1234567890, stream-time=(guint64)1234567890, running-time=(guint64)1234567890, duration=(guint64)40000000, score=(double)78.910751757633022, index=(int)26, type=(string)frame, ms-ssim=(double)0.96676034472760064, ssim=(double)0.8706783652305603, psnr-y=(double)30.758853484390933;

## Example launch line

     gst-launch-1.0 -m \
       filesrc location=test1.yuv ! rawvideoparse width=1920 height=1080 ! v.ref_sink  \
       filesrc location=test2.yuv ! rawvideoparse width=1920 height=1080 ! v.dist_sink \
       vmaf name=v frame-message=true results-filename=scores.json psnr=true ssim=true ms-ssim=true ! autovideosink \

This pipeline will output messages to the console for each set of compared frames.

## Hierarchy

    GObject
        ╰──GInitiallyUnowned
            ╰──GstObject
                ╰──GstElement
                    ╰──GstAggregator
                        ╰──GstVideoAggregator
                            ╰──vmaf

## Factory details

Authors: – Casey Bateman , Andoni Morales , Diego Nieto

Classification: – `Filter/Analyzer/Video`

Rank – none

Plugin – vmaf

Package – GStreamer Bad Plug-ins

## Pad Templates

### `dist_sink`

    video/x-raw:
             format: { I420, NV12, YV12, Y42B, Y444, I420_10LE, I422_10LE, Y444_10LE }
              width: [ 1, 2147483647 ]
             height: [ 1, 2147483647 ]
          framerate: [ 0/1, 2147483647/1 ]

Presence – always

Direction – sink

Object type – GstVideoAggregatorPad

### `ref_sink`

    video/x-raw:
             format: { I420, NV12, YV12, Y42B, Y444, I420_10LE, I422_10LE, Y444_10LE }
              width: [ 1, 2147483647 ]
             height: [ 1, 2147483647 ]
          framerate: [ 0/1, 2147483647/1 ]

Presence – always

Direction – sink

Object type – GstVideoAggregatorPad

### `src`

    video/x-raw:
             format: { I420, NV12, YV12, Y42B, Y444, I420_10LE, I422_10LE, Y444_10LE }
              width: [ 1, 2147483647 ]
             height: [ 1, 2147483647 ]
          framerate: [ 0/1, 2147483647/1 ]

Presence – always

Direction – src

Object type – GstAggregatorPad

## Properties

### conf-interval

    “conf-interval” gboolean

Enable confidence intervals

Flags : Read / Write

Default value : false

### disable-clip

    “disable-clip” gboolean

Disable clipping VMAF values

Flags : Read / Write

Default value : false

### enable-transform

    “enable-transform” gboolean

Enable transform VMAF scores

Flags : Read / Write

Default value : false

### frame-message

    “frame-message” gboolean

Enable frame level score messaging

Flags : Read / Write

Default value : false

### log-level

    “log-level” GstVmafLogLevel *

VMAF log level

Flags : Read / Write

Default value : none (0)

### model-filename

    “model-filename” gchararray

Model *.pkl abs filename, or file version for built in models

Flags : Read / Write

Default value : vmaf_v0.6.1

### ms-ssim

    “ms-ssim” gboolean

Estimate MS-SSIM

Flags : Read / Write

Default value : false

### phone-model

    “phone-model” gboolean

Use VMAF phone model

Flags : Read / Write

Default value : false

### pool-method

    “pool-method” GstVmafPoolMethod *

Pool method for mean

Flags : Read / Write

Default value : mean (3)

### psnr

    “psnr” gboolean

Estimate PSNR

Flags : Read / Write

Default value : false

### results-filename

    “results-filename” gchararray

VMAF results filename for scores

Flags : Read / Write

Default value : NULL

### results-format

    “results-format” GstVmafResultsFormat *

VMAF results file format used for scores (csv, xml, json)

Flags : Read / Write

Default value : none (0)

### ssim

    “ssim” gboolean

Estimate SSIM

Flags : Read / Write

Default value : false

### subsample

    “subsample” guint

Computing on one of every N frames

Flags : Read / Write

Default value : 1

### threads

    “threads” guint

The number of threads

Flags : Read / Write

Default value : 8

## Named constants

### GstVmafLogLevel

#### Members

`none` (0) – No logging
`error` (1) – Error
`warning` (2) – Warning
`info` (3) – Info
`debug` (4) – Debug

### GstVmafPoolMethod

#### Members

`min` (1) – Minimum value
`max` (2) – Maximum value
`mean` (3) – Arithmetic mean
`harmonic_mean` (4) – Harmonic mean

### GstVmafResultsFormat

#### Members

`none` (0) – None
`xml` (1) – XML
`csv` (3) – Comma Separated File (csv)
`json` (2) – JSON

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