Changes between Version 4 and Version 5 of Encode/AV1

Timestamp:

Jun 3, 2018, 6:25:06 PM (8 years ago)

Author:

slhck

Comment:

add 2-pass example

Encode/AV1

@@ -10 +10 @@
 
 - 1-pass average bitrate
+- 2-pass average bitrate
 - Constant quality
 
@@ -16 +17 @@
 {{{
 #!div style="border: 1px solid #e5e5c7; margin: 1em; background-color: #ffd;"
-'''Note:''' AV1 encoding is very slow in comparison to VP9 or H.264, and considered experimental at this stage.
+'''Note:''' AV1 encoding is very slow in comparison to VP9 or H.264, and considered experimental at this stage (hence the use of `-strict -2` is necessary).
 }}}
 
@@ -24 +25 @@
 
 {{{
-ffmpeg -i input.mp4 -c:v libaom-av1 -b:v 2M -strict -2 av1_test.mkv
+ffmpeg -i input.mp4 -c:v libaom-av1 -b:v 2M -strict -2 output.mkv
 }}}
 
 Use this option if file size and encoding time are more important.
+
+=== Two-Pass ===#twopass
+
+In order to create more efficient encodes when a particular target bitrate should be reached, you should choose two-pass encoding. For two-pass, you need to run `ffmpeg` twice, with almost the same settings, except for:
+
+* In pass 1 and 2, use the `-pass 1` and `-pass 2` options, respectively.
+* In pass 1, output to a null file descriptor, not an actual file. (This will generate a logfile that ffmpeg needs for the second pass.)
+* In pass 1, you need to specify an output format (with `-f`) that matches the output format you will use in pass 2.
+* In pass 1, specify the audio codec used in pass 2; in many cases, `-an` in pass 1 will not work.
+
+{{{
+ffmpeg -i input.mp4 -c:v libaom-av1 -strict -2 -b:v 2M -pass 1 -f matroska /dev/null && \
+ffmpeg -i input.mp4 -c:v libaom-av1 -strict -2 -b:v 2M -pass 2 output.mkv
+}}}
+
+{{{
+#!div style="border: 1px solid #e5e5c7; margin: 1em; background-color: #ffd;"
+'''Note:''' Windows users should use `NUL` instead of `/dev/null` and `^` instead of `\`.
+}}}
 
 === Constant Quality ===#constantq