Changes between Version 3 and Version 4 of Waveform

Timestamp:

Dec 27, 2015, 10:18:54 PM (10 years ago)

Author:

llogan

Comment:

add showwaves 'n friends

Waveform

@@ -1 +1 @@
 [[PageOutline(1-100,Contents)]]
 
-= Overview =
-
 Audio data is often represented by a waveform image. This guide explains how to
-easily create such an image using FFmpeg and Gnuplot.
-
-= Single Channel =
+easily create such an image or video.
+
+= Waveform image =
+
+The [https://ffmpeg.org/ffmpeg-filters.html#showwavespic showwavespic] filter is the easiest method to create a waveform image.
+
+== All channels ==
+
+[[Image(showwavespic.png)]]
+
+{{{
+ffmpeg -i input -filter_complex "showwavespic=s=640x120" -frames:v 1 output.png
+}}}
+
+All channels will be represented by various shades in the waveform.
+
+== Downmixed ==
+
+[[Image(showwavespic_mono.png)]]
+
+If you want a simpler representation where all channels are represented by one waveform you can downmix your audio to mono first with [https://ffmpeg.org/ffmpeg-filters.html#aformat aformat]:
+
+{{{
+ffmpeg -i input -filter_complex "aformat=channel_layouts=mono,showwavespic=s=640x120" -frames:v 1 output.png
+}}}
+
+== Separate channels ==
+
+[[Image(showwavespic_split.png)]]
+
+If you want to split them into separate channels:
+
+{{{
+ffmpeg -i input -filter_complex "showwavespic=s=640x240:split_channels=1" -frames:v 1 output.png
+}}}
+
+== Changing range ==
+
+[[Image(showwavespic_compand.png)]]
+
+If the waveform looks a little flat you can use the [https://ffmpeg.org/ffmpeg-filters.html#compand compand] filter to expand or compress the dynamic range:
+
+{{{
+ffmpeg -i input -filter_complex "compand,showwavespic=s=640x120" -frames:v 1 output.png
+}}}
+
+Note that this won't be as accurate of a representation as it would without compand, but for aesthetics it may be preferred.
+
+== Adding color, alpha (transparency), and background ==
+
+Using [https://ffmpeg.org/ffmpeg-filters.html#format format], [https://ffmpeg.org/ffmpeg-filters.html#colorkey colorkey], [https://ffmpeg.org/ffmpeg-filters.html#colorchannelmixer colorchannelmixer], and [https://ffmpeg.org/ffmpeg-filters.html#overlay overlay]:
+
+{{{
+ffmpeg -i input -i background.png -filter_complex \
+"[0:a]showwavespic=s=640x240,format=rgba,colorkey=black,colorchannelmixer=rr=0.953:gg=0.435:bb=0.133[top]; \
+ [1:v][top]overlay=format=rgb" \
+-frames:v 1 output.png
+}}}
+
+* This example assumes the background is the same width and height as the waveform. If it is not, you can [https://ffmpeg.org/ffmpeg-filters.html#scale scale], [https://ffmpeg.org/ffmpeg-filters.html#crop crop], or [https://ffmpeg.org/ffmpeg-filters.html#pad pad] the background first.
+
+* This example will make the waveform an orange color (`#f36f22` or `rgb(243,111,34)`). The RGB value for each color channel must be interpolated to fit the 0-1 range of the colorchannelmixer filter by dividing each value by 255. For example, the green channel is 111/255≈0.435.
+
+= Waveform video =
+
+[[Image(showwaves.png)]]
+
+The [https://ffmpeg.org/ffmpeg-filters.html#showwaves showwaves] filter makes a video waveform.
+
+{{{
+ffmpeg -i input -filter_complex "[0:a]showwaves=s=1280x720:mode=line,format=yuv420p[v]" -map "[v]" -map 0:a -c:v libx264 -c:a copy output.mkv 
+}}}
+
+----
+
+= Using Gnuplot =
+
+== Single Channel ==
 
 Plotting a single channel waveform is easier as the data can be passed to
@@ -96 +169 @@
 
 
-= Multiple Channels =
+== Multiple Channels ==
 
 While the basic idea and the command for plotting multiple channels remain the
@@ -140 +213 @@
 
 
-= Additional Hints =
+== Additional Hints ==
 
 Sometimes there are a few loud pitches while the rest of the data is relatively