FFmpeg - Encode VP9: Difference between revisions

Latest revision as of 15:55, 14 March 2026

VP9 is Google’s open, royalty‑free video codec designed to deliver high compression efficiency and excellent visual quality at lower bitrates. When encoding VP9 with FFmpeg’s libvpx-vp9 encoder, two-pass encoding is generally recommended. Some of VP9’s quality‑enhancing features are only available in multi-pass mode, and two-pass encoding allows the encoder to make better bitrate allocation decisions across the entire file.

Why Two-Pass Encoding?

Two-pass encoding provides FFmpeg with full knowledge of the input before performing the final encode. This enables:

Better quality at a target size
Access to quality-enhancing algorithms
More predictable output quality

Constant Quality Mode (CRF)

Unlike constant bitrate encoding, CRF mode prioritises visual quality. To invoke CRF mode in VP9:

Set -b:v 0
Select a CRF value (lower = higher quality)

Typical CRF ranges:

CRF	Quality Level	Typical Use
15–25	High quality	Archival, production masters
28–32	Good quality	General-purpose encoding, streaming
33–40	Low bitrate	Mobile, constrained bandwidth

Two-Pass VP9 Encoding (CRF + Bitrate 0)

Linux / macOS

ffmpeg -i input.file -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 1 -an -f null /dev/null && ffmpeg -i input.file -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 2 -c:a libopus output.webm

Windows

ffmpeg -i input.file -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 1 -an ^
    -f null NUL ^
    && ffmpeg -i input.file -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 2 ^
    -c:a libopus output.webm

Audio Encoding

Recommended:

-c:a libopus -b:a 96k

Recommended Additional Options

Option	Meaning
-row-mt 1	Enables row-based multi-threading
-tile-columns 2	Enables parallel decode paths
-tile-rows 1	Further decode parallelism
-g 240	GOP size

Encoding Time vs Quality

VP9 is CPU-intensive. Raising -speed can reduce encoding time:

-speed 1 — best quality
-speed 2 — faster
-speed 3 — acceptable for many workflows

Troubleshooting

Low CPU Usage

Check:

-row-mt 1
-threads N

Output File Is Very Large

Increase CRF:

-crf 32

Audio Missing After First Pass

Expected. Audio is encoded only in pass 2.

References

https://trac.ffmpeg.org/wiki/Encode/VP9

@@ Line 1: / Line 1: @@
 [[Category:FFmpeg]]
 [[Category:VP9]]
-Two-pass is the recommended encoding method for libvpx-vp9 as some quality-enhancing encoder features are only available in 2-pass mode.<br/>
+VP9 is Google’s open, royalty‑free video codec designed to deliver high compression efficiency and excellent visual quality at lower bitrates. When encoding VP9 with FFmpeg’s libvpx-vp9 encoder, two-pass encoding is generally recommended. Some of VP9’s quality‑enhancing features are only available in multi-pass mode, and two-pass encoding allows the encoder to make better bitrate allocation decisions across the entire file.
-Constant quality 2-pass is invoked by setting <code>-b:v</code> to <code>zero</code> and specifying a quality level using the <code>-crf</code> switch:<br/>
+== Why Two-Pass Encoding? ==
+Two-pass encoding provides FFmpeg with full knowledge of the input before performing the final encode. This enables:
+* Better quality at a target size
+* Access to quality-enhancing algorithms
+* More predictable output quality
+== Constant Quality Mode (CRF) ==
+Unlike constant bitrate encoding, CRF mode prioritises visual quality. To invoke CRF mode in VP9:
+* Set -b:v 0
+* Select a CRF value (lower = higher quality)
+Typical CRF ranges:
+{| class="wikitable"
+! CRF !! Quality Level !! Typical Use
+|-
+| 15–25 || High quality || Archival, production masters
+|-
+| 28–32 || Good quality || General-purpose encoding, streaming
+|-
+| 33–40 || Low bitrate || Mobile, constrained bandwidth
+|}
+== Two-Pass VP9 Encoding (CRF + Bitrate 0) ==
+=== Linux / macOS ===
 <pre>
-ffmpeg -i <input.file> -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 1 -an -f null /dev/null && \
+ffmpeg -i input.file -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 1 -an -f null /dev/null && ffmpeg -i input.file -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 2 -c:a libopus output.webm
-ffmpeg -i <input.file> -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 2 -c:a libopus <output.file>
 </pre>
-Note: Windows users should use <code>NUL</code> instead of <code>/dev/null</code> and <code>^</code> instead of <code>\</code>.
-Reference: [[https://trac.ffmpeg.org/wiki/Encode/VP9 FFmpeg: FFmpeg and VP9 Encoding Guide]]
+=== Windows ===
+<pre>
+ffmpeg -i input.file -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 1 -an ^
+    -f null NUL ^
+    && ffmpeg -i input.file -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 2 ^
+    -c:a libopus output.webm
+</pre>
+== Audio Encoding ==
+Recommended:
+<pre>
+-c:a libopus -b:a 96k
+</pre>
+== Recommended Additional Options ==
+{| class="wikitable"
+! Option !! Meaning
+|-
+| -row-mt 1 || Enables row-based multi-threading
+|-
+| -tile-columns 2 || Enables parallel decode paths
+|-
+| -tile-rows 1 || Further decode parallelism
+|-
+| -g 240 || GOP size
+|}
+== Encoding Time vs Quality ==
+VP9 is CPU-intensive. Raising -speed can reduce encoding time:
+* -speed 1 — best quality
+* -speed 2 — faster
+* -speed 3 — acceptable for many workflows
+== Troubleshooting ==
+=== Low CPU Usage ===
+Check:
+<pre>
+-row-mt 1
+-threads N
+</pre>
+=== Output File Is Very Large ===
+Increase CRF:
+<pre>
+-crf 32
+</pre>
+=== Audio Missing After First Pass ===
+Expected. Audio is encoded only in pass 2.
+== References ==
+* https://trac.ffmpeg.org/wiki/Encode/VP9

FFmpeg - Encode VP9: Difference between revisions

Latest revision as of 15:55, 14 March 2026

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