Convert OGV to MP4
OGV is Ogg Video - Theora video plus Vorbis audio in the Ogg container. It plays in Firefox and Chrome but almost nowhere else. Wave re-encodes locally to a plain MP4 that plays on Safari, iOS, and every consumer device.
What actually changes
Ogg was designed as a royalty-free alternative to MPEG and became the default video format on Wikipedia and old MDN samples. Its two codecs - Theora for video, Vorbis for audio - are open-source and license-clean, but MP4 accepts neither. That means an OGV-to-MP4 conversion is always a full re-encode; there is no fast-copy path.
Wave decodes the Theora frames and Vorbis samples through the on-device ffmpeg engine, then re-encodes video to H.264 through the browser's WebCodecs encoder when your browser exposes one (most Chrome / Edge / Safari installs do), or falls back to MPEG-4 Part 2 otherwise. Audio always re-encodes to AAC at 192 kbps. A small subset of .ogv files carry VP8 video instead of Theora - those are effectively WebM in a different wrapper, and the WebCodecs path handles them the same way.
Three steps.
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Step 1
Drop the OGV file onto the card.
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Step 2
Wave shows Re-encode needed - Theora and Vorbis can't sit inside an MP4.
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Step 3
Convert and save the MP4.
Answers, specifically.
Why doesn't OGV play on iPhones?
Apple has never shipped a Theora decoder on iOS or macOS. Chrome and Firefox added Theora playback around 2010 as part of the html5 video push; every other platform sidestepped it. Converting to H.264 in an MP4 is the pragmatic fix.
Is this lossless?
No. Any transcode between two lossy codecs (Theora → H.264) loses a small amount of fidelity. Wave targets a high-quality bitrate, and the loss is imperceptible on almost any content you'd reasonably watch.
What about .ogg files with video inside?
Same story. The Ogg container carries both audio-only .ogg (Vorbis) and video .ogv. If you drop a video-bearing .ogg onto Wave, it works - Wave inspects the streams, not the extension.
Where do OGV files even come from these days?
Wikipedia media (before the WebM migration), some open-source video archives, and old MDN / W3C demos. If you've downloaded video from an educational site older than about 2015, it's often OGV.
Will the file be larger or smaller?
Similar. Theora and H.264 have comparable per-bit efficiency for typical content; the MP4 usually lands within 10–15 % of the source size at Wave's default quality.