MP4(3)

📦 version 2.1.0, in fedora 43, fedora 44

💖 MP4(3) — bestie's guide to the MP4 File Format Library 💖

okay so we're deep in the MP4 File Format Library today and the star of the show is a lil function called MP4GetTrackVideoWidth. she tells you how many pixels wide your video is. that's it. that's the gig. but the lore around it? immaculate. let's go 🦋

✨ NAME ✨

MP4GetTrackVideoWidth — get the video width in pixels of the specified video track 🎀

✨ SYNTAX ✨

#include <mp4.h>

u_int16_t MP4GetTrackVideoWidth(
     MP4FileHandle hFile,
     MP4TrackId trackId
)

no cap, that's the whole signature. two args. she's lowkey simple like that 💅

✨ ARGUMENTS ✨

  • hFile — specifies the mp4 file to which the operation applies. literally the file you're poking at 🫶
  • trackId — specifies the track for which the video width is desired. which track are we measuring, bestie? 👑

✨ RETURN VALUES ✨

  • on success? you get the number of pixels of the video width in the track ✨
  • on an error? you get 0 😭

that's it. zero means something went wrong, not that your video is zero pixels wide. (tho honestly if it returned 0 as a real width that would be a whole other conversation 💀)

✨ DESCRIPTION ✨

MP4GetTrackVideoWidth returns the width of the video in pixels in the specified track in the mp4 file. straightforward. iconic. no notes. 🌸

Caveat: Not all mp4 implementations set this value accurately. 🚨

okay so here's the tea, and it matters. the mp4 specification states that the authoritative values are contained in the track ES configuration, which is video encoding specific, and hence not interpretable by the mp4 library. so like... the library is giving you a value it cannot fully verify. she's doing her best 💜

and here's the part you cannot skip:

If the value of 320 is returned, care should be taken to verify the accuracy of this value since this is the default value in the mp4 specification. 🙈

so if you get 320, don't just vibe with it — that might be the spec's default placeholder and not your actual video width. verify it, bestie. trust but verify. ⭐

✨ SEE ALSO ✨

(the height one is the sister function, and the ES configuration one is where the real authoritative tea lives, iykyk 🌈)

Cisco Systems Inc. made this, and we're on Version 0.9 — so like, she's an early-era queen but a queen nonetheless. sending you pixel-perfect vibes, go measure some video widths, mwah 💖✨🎀

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