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by zerocrates
3304 days ago
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It mentions that it supports not only sequences but inter-frame prediction (so P- and possibly B- frames I assume), which is sort of surprising to me but of course makes sense especially given Apple's "image burst" usage. I'm also suprised to learn that WebP apparently supports P-frames in its animations. What's really different between this and the existing usages of the MP4 container for images, though? Is it just the packaging as an "image" format, or specification of more image-y metadata? |
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You are right -- the main difference is that BMFF was originally designed for time-based media (video, audio) but isn't in itself well suited towards media that isn't time based, like images and their associated metadata (e.g. Exif).
HEIF extends the ISO BMFF so that you can have untimed media -- one or more photos, a collection -- or even mixed media comprising both untimed and timed media. Apple's live photo is a good example of mixed media, comprising a photo and a video.
But the HEIF container format goes so much further. You could have image sequences -- for example a higher-quality version of Animated GIF (using I-frames only, or P/B for more compression) with looping -- tiling, auxiliary images like depth maps and alpha channels, or even stereo images with a left and right channel.
Though originally HEIF came out of the HEVC standards track, hence the words "High Efficiency" in the name, it was later extended to include other codecs like JPEG, AVC. There's no reason it couldn't be extended to include VP9, PNG, or any other codec.
Think of HEIF as a versatile, extensible, standardized container format. The media coding scheme is separable. This is a big deal for the future of image/media coding because we're no-longer locked into "yet another format" that's tied to the codec. With the ISO BMFF box model, HEIF can grow to adapt new constructs and codecs for some generations to come.