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media: H.264 fallback beside every AV1, and the post links the H.264
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The AV1-only publish lasted four hours in the wild: the first viewer on
mobile Safari got "bad media error" from the raw file, because a post's
link is fetched raw — Lemmy apps and browsers play that exact URL, with
no <source> negotiation in front of it. The previous commit's note
("--raw ... if that audience matters") had it backwards: the audience
that cannot play AV1 is not a per-post judgement call, it is whoever
happens to open the thread on an iPhone.

So publish-media.sh now emits two encodings and points the post at the
compatible one:

  * Every video transcode also produces <hash>.h264.mp4 (x264 crf 23,
    same denoise, same frames), uploaded beside the AV1 under the AV1's
    hash — the poster's sibling-naming trick, reused, so fetch-media.sh
    finds it by name with nothing to look up.
  * The printed URL to paste into the post is the H.264 one. pict-rs
    can thumbnail it too, so instance thumbnails come back as a bonus.

fetch-media.sh adopting an own-origin .h264.mp4 URL swaps the AV1 back
in as the page's primary when it is on the mount, and records the H.264
as `fallback` in posts.json. The renderer turns a non-empty fallback
into a <source> pair: the AV1 first with an explicit codecs parameter —
both files are video/mp4, so the parameter is the only thing that lets
a non-AV1 browser skip to the file it can play — and the H.264 second.
Browsers with AV1 keep downloading the small file; Safari before 17
gets one that plays instead of an element that will not.

e2e gains the matching conditional gate: a page offering an av01
<source> must offer an .h264.mp4 one, so an AV1 video can never again
ship without its fallback.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Jorijn van der Graaf 2026-08-08 03:14:51 +02:00
commit a625176c7d
6 changed files with 142 additions and 25 deletions
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27
shared/interfaces/Catcrafts.Shared-Views.cppm
View file

@ -353,10 +353,29 @@ SafeHtml RenderPostMedia(std::span<const PostMedia> media) {
: SafeHtml{};
if (m.kind == "video") {
SafeHtml poster = m.poster.empty() ? SafeHtml{} : Url("poster", m.poster);
items.push_back(Format(
R"(<video class="post-media__item" controls preload="metadata" )"
R"(playsinline{}{}{}></video>)",
Url("src", m.src), poster, dims));
if (m.fallback.empty() || m.fallback == m.src) {
items.push_back(Format(
R"(<video class="post-media__item" controls preload="metadata" )"
R"(playsinline{}{}{}></video>)",
Url("src", m.src), poster, dims));
} else {
// An AV1 video with its H.264 rendition. Both are .mp4, so the
// container alone cannot tell them apart: the codecs parameter
// on the first <source> is what lets a browser without AV1
// (Safari before 17, Apple hardware without the decoder) skip
// it and take the H.264 instead of failing on a file it cannot
// decode. The string is advisory and used only for selection —
// once a source is picked the browser reads the actual stream —
// so the canonical profile-0 8-bit form is right for anything
// publish-media.sh emits (yuv420p is pinned there).
items.push_back(Format(
R"(<video class="post-media__item" controls preload="metadata" )"
R"(playsinline{}{}>)"
R"(<source{} type="video/mp4; codecs=av01.0.08M.08">)"
R"(<source{} type="video/mp4">)"
R"(</video>)",
poster, dims, Url("src", m.src), Url("src", m.fallback)));
}
} else {
// alt is empty and aria-hidden is absent on purpose: these are
// screenshots whose meaning is already in the post title and