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Create short practice clips from any video. Loop movements, tag techniques, and build your personal library.

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Engineering notesVolume 6 of 8 · Practice
Volume 6

Practice by the Frame

Dancers learn by watching eight seconds of someone else two hundred times. YouTube gives them a scrub bar and a spinner. This is how any moment of any performance becomes a clip that loops without a flicker, slows to quarter speed, mirrors, steps one frame at a time, and comes back on the day you would have forgotten it.

a clip
2–300 sa clip
speed
¼× to 2×speed
the swap nobody sees
80 msthe swap nobody sees
one frame
1/30 sone frame
seconds of video we store
0seconds of video we store

Part 01

A clip is two numbers and a few words

a studentthe performance · 3:091:071:16the clipstart 67 · end 76 · speed ½“back sacada into the turn”tags: sacada · giro · privateinherited, for freeQuiñones & Piliu“La milonga de Buenos Aires” · CanaroTangoLovers Festival · Athens · 2018The footage stays on YouTube. Nine seconds of a performance become one row,and every catalog fact about the video applies to it.
Two markersScrub in and out against the live player. Two to three hundred seconds.
A row, not a fileStart, end, a title, up to five movement tags from a shared vocabulary, a preferred speed.
Everything comes alongFilter the practice library by dancer, band, festival or genre without tagging anything.

TangoTube does not host video, so a clip cannot be a copy. It is a reference to a moment. That is what makes it free to make, free to store, and instantly connected to everything the catalog already knows. Clips are private by default: a study note first, a publication only if the person who cut it says so.

Part 02

Two players, one seam you cannot see

A · playingwhat you seeB · hidden, muted, waiting at the startthe clip80 ms before the endB · playingalready loaded, starts instantly1 · B starts and becomes visible; A fades out2 · a moment later A is muted, sent back to the start, paused3 · A is now the one waiting. Repeat.No spinner. No uploader’s thumbnail flashing. No jump.Slow motion stays slow through the swap: the speed is set on both.A–B markers just replace the start and end in step 1. Nothing else changes.
Two black boxesThe video player is YouTube's and cannot be changed. So there are two of them, stacked.
The swapEighty milliseconds before the end, scaled to the speed, the hidden one starts. Humans see continuity.
Roles tradeThe one that just finished goes quiet, rewinds, and waits. Loop forever.

A single embedded player cannot loop cleanly: rewinding shows a spinner and an overlay, and at half speed the gap is a whole beat of music. The lead time is the entire trick. Too short and the second player has not started; too long and the last frames are lost. Eighty milliseconds is where people see nothing.

Part 03

Slower, mirrored, one frame at a time

¼×speedset on both playersmirror · flips the frame◁ 1/30 s ▷frame steppause · seek · showABA–B · loop inside a clip3 s of a 12 s clipComparetwo couples, same movement, side by side or one after the otherfound on the collection page for that movement: “Sacada · 23 clips from 18 dancers”A loop counter shows the repetition you are on, because knowing it is the fortieth is part of practising honestly.
Each tool is a transformOn the player or on the frame around it. The player never knows.
One frame wideThe moment a lead begins lives in a single frame. No scrub bar can find it.
CompareSame movement, different couples. Nobody else would build this; it is how tango is learned.

A study mode holds every clip at half speed for a whole session. Mirror flips the frame so a follower learning from a leader’s video sees the movement as they would in a mirror. None of it touches the footage, because none of it can.

Part 04

Come back on the day you would have forgotten

a clip you saved for practiceis a card in your deckday 0againday 1hardday 4easyday 12easyday 38The gap grows when you know it and collapses when you do not.The same scheduling that has run language flashcards for forty years, applied to eight seconds of someone’s feet.
CardsEvery clip you save is one. Drill only sacadas today, or everything that is due.
Three buttonsAgain, hard, easy. The answer sets when the clip returns.
Scheduled by memoryNot by mood. The clip you rated hard last week comes back before the one you rated easy yesterday.

Without a scheduler, people rewatch what they enjoy and neglect what they need. With one, the library reports its own weak spots: the movements with the lowest ease across your deck. Nobody has to cut their own clips; any public clip can be saved into any deck, so one careful student’s clip becomes a card in a hundred decks.

Part 05

Leave the site without leaving the catalog

a public clipa blog postembedded, loopingnames the dancersa pasted linkunfurls into a playernames the recordingswipe ↑the shorts feedevery copy is a door back to the whole performance and the catalog behind it
EmbedA layout-free player at a stable address any blog or forum can carry, with autoplay, loop and mute as switches.
UnfurlPaste the link in a chat and it becomes a looping player with the dancers and recording named beneath.
ShortsFull-screen clips, swipe to advance, tags tappable, one link back to the whole dance.

The shorts feed is ordered the way Volume 5 orders everything: clips of dancers you watch, then clips with tags you like, then what is trending this week, then what is new. It is the lowest-commitment way into tango that exists, and every clip in it is nine seconds from a fully catalogued performance. Playlists do the same job at the scale of whole performances, and the player keeps playing in a small frame as you move around the site.

Take-aways, without the tango

  1. 01Find the real unit of use. The moment, not the file. A reference to it costs nothing and inherits everything.
  2. 02When the platform is a black box you cannot modify, use two of them and choose which one to show.
  3. 03Build tools as transforms on the frame around the box, so the box never has to know.
  4. 04Borrow a forty-year-old scheduling algorithm instead of inventing a recommendation engine for practice.
  5. 05Make everything embeddable, and make every embed a door back to the catalog.

The Cabeceo

We've caught your eye across the milonga. Like any good tango, this starts with consent — nothing optional runs until you say so. What we store