Generating a waveform using ffmpeg

Question

I am trying to generate a waveform image using ffmpeg.

I have successfully made a waveform image, however it doesn't look very nice...

I have been looking around to try and style the image to make it look nicer, however I have been unable to find any information on this or any tutorials on this.

I am using PHP and shell_exec to create the waveform.

I am aware that there are php library that can do this but due to file format this is a lengthy process.

The code I am using is as follows:

$command = 'convertvid\bin\ffmpeg -i Temp\\'.$file.' -y -lavfi showwavespic=split_channels=0:s='.$width.'x50 Temp\\'.$PNGFileName;
shell_exec($command);

Basically I would like to add a line through the middle as there are blank spots at the moment and would like to be able to set the background and wave colour.

Solution

Default waveform

ffmpeg -i input.wav -filter_complex showwavespic -frames:v 1 output.png

Notes

• Notice the segment of silent audio in the middle (see "Fancy waveform" below if you want to see how to add a line).

• The background is transparent.

• Default colors are red (left channel) and green (right channel) for a stereo input. The color is mixed where the channels overlap.

• You can change the channel colors with the colors option, such as "showwavespic=colors=blue|yellow". See a list of valid color names or use hexadecimal notation, such as #ffcc99.

• See the showwavespic filter documentation for additional options.

• If you want a video instead of an image use the showwaves filter.

Fancy waveform

ffmpeg -i input.mp4 -filter_complex \
"[0:a]aformat=channel_layouts=mono, \
 compand=gain=-6, \
 showwavespic=s=600x120:colors=#9cf42f[fg]; \
 color=s=600x120:color=#44582c, \
 drawgrid=width=iw/10:height=ih/5:color=#[email protected][bg]; \
 [bg][fg]overlay=format=auto,drawbox=x=(iw-w)/2:y=(ih-h)/2:w=iw:h=1:color=#9cf42f" \
-frames:v 1 output.png

Explanation of options

1. aformat downsamples the audio to mono. Otherwise, by default, a stereo input would result in a waveform with a different color for each channel (see Default waveform example above).

2. compand modifies the dynamic range of the audio to make the waveform look less flat. It makes a less accurate representation of the actual audio, but can be more visually appealing for some inputs.

3. showwavespic makes the actual waveform.

4. color source filter is used to make a colored background that is the same size as the waveform.

5. drawgrid adds a grid over the background. The grid does not represent anything, but is just for looks. The grid color is the same as the waveform color (#9cf42f), but opacity is set to 10% (@0.1).

6. overlay will place [bg] (what I named the filtergraph for the background) behind [fg] (the waveform).

7. Finally, drawbox will make the horizontal line so any silent areas are not blank.

Gradient example

Using gradients filter:

ffmpeg -i input.mp3 -filter_complex "gradients=s=1920x1080:c0=000000:c1=434343:x0=0:x1=0:y0=0:y1=1080,drawbox=x=(iw-w)/2:y=(ih-h)/2:w=iw:h=1:color=#0000ff[bg];[0:a]aformat=channel_layouts=mono,showwavespic=s=1920x1080:colors=#0068ff[fg];[bg][fg]overlay=format=auto" -vframes:v 1 output.png

Color background

ffmpeg -i input.opus -filter_complex "color=c=blue[color];aformat=channel_layouts=mono,showwavespic=s=1280x720:colors=white[wave];[color][wave]scale2ref[bg][fg];[bg][fg]overlay=format=auto" -frames:v 1 output.png

The scale2ref filter automatically makes the background the same size as the waveform.

Image background

Of course you can use an image or video instead for the background:

ffmpeg -i audio.flac -i background.jpg -filter_complex \
"[1:v]scale=600:-1,crop=iw:120[bg]; \
 [0:a]showwavespic=s=600x120:colors=cyan|aqua[fg]; \
 [bg][fg]overlay=format=auto" \
-q:v 3 showwavespic_bg.jpg

---

Getting waveform stats and data

Use the astats filter. Many stats are available: RMS, peak, min, max, difference, etc.

RMS level per audio frame

Example to get standard RMS level measured in dBFS per audio frame:

ffprobe -v error -f lavfi -i "amovie=input.wav,astats=metadata=1:reset=1" -show_entries frame_tags=lavfi.astats.Overall.RMS_level -of csv=p=0 > rms.log

Peak level per second

Add the asetnsamples filter.

ffprobe -v error -f lavfi -i "amovie=input.wav,asetnsamples=44100,astats=metadata=1:reset=1" -show_entries frame_tags=lavfi.astats.Overall.Peak_level -of csv=p=0

Same as above but with timestamps

ffprobe -v error -f lavfi -i "amovie=input.wav,asetnsamples=44100,astats=metadata=1:reset=1" -show_entries frame=pkt_pts_time:frame_tags=lavfi.astats.Overall.Peak_level -of csv=p=0

Output to file

Just append > output.log to the end of your command:

ffprobe -v error -f lavfi -i "amovie=input.wav,asetnsamples=44100,astats=metadata=1:reset=1" -show_entries frame_tags=lavfi.astats.Overall.RMS_level -of csv=p=0 > output.log

JSON

ffprobe -v error -f lavfi -i "amovie=input.wav,asetnsamples=44100,astats=metadata=1:reset=1" -show_entries frame_tags=lavfi.astats.Overall.RMS_level -of json > output.json

Comments

[Jeff]

Thanks LongNeckbeard, you are the FFmpeg master! When I did "boring default wav" command it already had a transparent background and red wave, i didn't have to add the extra stuff which works great.

[chovy]

Option 'colors' not found -- i assume i need a build flag

[llogan]

@chovy Your ffmpeg is too old. See the FFmpeg Download page for links to "static builds" for your OS.

[Ankush]

@llogan is there a way to generate waveform data in an array format, so that it can be plotted manually?

[llogan]

@Ankush Can you show my an example of what you want?

[Ankush]

@llogan So what I am trying to do is, In Android, I am trying to make a UI that shows one streak for every second of the audio clip. So I was wondering if there's a way to get an array of amplitudes (average) per second. For example, if a clip is 10 seconds long, I want an array of 10 size where each element is the amplitude for every second. Then I can manually plot these 10 array elements in a UI. Have a look at this image and hover over it for viewing comments drive.google.com/file/d/1u375nXkVe8ekiMbQToVNGekgAgLujKjj/vi‌​ew

[llogan]

@Ankush Assuming an input with a 44100 sample rate try ffprobe -v error -f lavfi -i amovie=input.wav,asetnsamples=44100,astats=metadata=1:reset=‌​1 -show_entries frame_tags=lavfi.astats.Overall.RMS_level -of csv=p=0 See astats filter for other stats to choose from.

[Ankush]

@llogan Thanks for the response. I'll check it out and will update in case of any queries. Thanks once again.

[Jérémy]

What if we don't want a picture of the waveform, but rather the raw output file using -f data? Which extension should we put? I always got "Unable to find a suitable output format for ..." no matter the output format. I ideally want it as a JSON, but raw data would be fine.

[llogan]

@Jérémy See the "RMS level per audio frame" command in the answer, but change -of csv=p=0 > rms.log to -of json > output.json