MP4(3)

💖 MP4(3) — MP4 File Format Library 💖

okay bestie, sit down, hydrate, and let me tell you about MP4SetTrackEditMediaStart — it lives in the MP4 File Format Library and it's literally the glow-up button for a track edit segment's media start time. ✨

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🌸 NAME 🌸

MP4SetTrackEditMediaStart — set the media start time of a track edit segment 🎬

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✨ SYNTAX ✨

#include <mp4.h>

bool MP4SetTrackEditMediaStart(
     MP4FileHandle hFile,
     MP4TrackId trackId,
     MP4EditId editId,
     MP4Timestamp mediaStartTime
);

no cap, that's the whole signature, character for character, we don't edit the queen's source code 💅

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🎀 ARGUMENTS 🎀

• hFile — the mp4 file this operation applies to. like, which file are we touching, bestie 🫶
• trackId — the track this operation applies to. pick your fave lane 🛤️
• editId — the edit segment this operation applies to. 🚨 caveat alert 🚨 the first edit has id 1, not 0. not me almost starting at zero 🙈
• mediaStartTime — the new value for the media start, in track time scale units. units matter, always check units, iykyk ⏱️

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💫 RETURN VALUES 💫

• on success: true (1) — slay, we ate 💅
• on error: false (0) — it's giving tragic, try again 😭

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🦋 DESCRIPTION 🦋

MP4SetTrackEditMediaStart sets the media start time of the specified edit segment from the specified track, in track time scale units. 🎯

need to map that value in from some other time scale? go see MP4ConvertToTrackTimestamp() for how to do that. she's the converter bestie, she handles the math 💖

and now the part that trips literally everyone: this is NOT the same thing as the edit segment start time. they're different values, different vibes, do not conflate them. for example:

EditId    Start     MediaStart     Duration
1         0         15             30
2         30        120            20
3         50        3000           10

see how Start and MediaStart are just... not the same column? yeah. that's the whole point. 🔥

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🌈 SEE ALSO 🌈

• MP4(3)
• MP4GetTrackEditMediaStart(3)

(the getter to this setter, obviously — they're a matched set, main character energy 👑)

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reminder bestie: editId starts at 1, and mediaStartTime is in track time scale units. two tiny things, zero regrets if you remember them 🎀

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Cisco Systems Inc. made this, it's Version 0.9, and it's filed under the MP4(3) manual. mwah, that's the whole page, go forth and set those media start times 💅💖✨