{"id":77,"date":"2015-01-10T13:19:45","date_gmt":"2015-01-10T13:19:45","guid":{"rendered":"http:\/\/johnwarburton.net\/blog\/?p=77"},"modified":"2015-08-09T16:38:11","modified_gmt":"2015-08-09T15:38:11","slug":"real-time-visual-pitch-display","status":"publish","type":"post","link":"https:\/\/johnwarburton.net\/blog\/?p=77","title":{"rendered":"Real-time visual pitch display"},"content":{"rendered":"

Here’s a hypnotic (or nausea-inducing) way of watching and listening to BBC radio programmes. You’ll need a modern version of FFplay, the multi-media player that’s part of the FFmpeg suite, and the open-source “get_iplayer” program. The filter that does the work is called “showcqt”.<\/p>\n

For this example, I’m using BBC Radio 3. You will, no doubt, see how the command line can be modified to accept any audio source.<\/p>\n

Just type this. This is from a Cygwin command line, rather similar to Unix. Windows won’t be much different.<\/p>\n

get_iplayer --stream --type=liveradio \"BBC Radio 3\" | ffplay -f lavfi \"amovie='pipe\\:0',asplit[a][b];[a]showcqt=fullhd=0:timeclamp=0.3:fps=30[out0]; [b]anull[out1]\"<\/code><\/p>\n

Or, as another example, here’s one of my favourite on-line streams, “The Departure Lounge”:<\/p>\n

ffplay.exe\" -f lavfi \"amovie='http\\:\/\/listen64.radionomy.com\/TheDepartureLounge',asplit[a][b];[a]showcqt=fullhd=0:timeclamp=0.3:fps=30[out0]; [b]anull[out1]\"<\/code><\/p>\n

…and, after waiting a few seconds for buffering, you’ll get this:<\/p>\n

\"Audio<\/a>
Audio spectrum of a fragment of a song for soprano and piano, with turntable rumble visible in the lower frequencies<\/figcaption><\/figure>\n

The backslash in the “pipe\\:0” is because colons must be escaped with a backslash in FFmpeg\/FFplay filters.<\/p>\n

Just out of interest, I have a Python project that outputs a handy video and audio scope that needs a little refinement, but you can download it here: https:\/\/github.com\/Warblefly\/FFmpeg-Scope\/<\/a><\/p>\n

The scope’s on-screen display includes a waveform monitor showing superimposed YUV levels with 16-235 markers to check BT601\/709 broadcast limits, an EBU R128 loudness chart, a stereo audio sum\/difference display, a colour vectorscope, a full-range video check monitor and timecode.<\/p>\n

This is the kind of output it gives:<\/p>\n

\"Screenshot<\/a>
Screenshot of FFmpeg scope<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

Here’s a hypnotic (or nausea-inducing) way of watching and listening to BBC radio programmes. You’ll need a modern version of FFplay, the multi-media player that’s part of the FFmpeg suite, and the open-source “get_iplayer” program. The filter that does the work is called “showcqt”. For this example, I’m using BBC Radio 3. You will, no … Continue reading Real-time visual pitch display<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,3],"tags":[],"class_list":["post-77","post","type-post","status-publish","format-standard","hentry","category-encoding","category-film-making"],"_links":{"self":[{"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/77","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=77"}],"version-history":[{"count":17,"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/77\/revisions"}],"predecessor-version":[{"id":26367,"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/77\/revisions\/26367"}],"wp:attachment":[{"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=77"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=77"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/johnwarburton.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=77"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}