Convert OGV to MP4
OGV files hold "Ogg Video" - video compressed with a format called Theora and audio compressed with Vorbis. Both are open-source formats designed as royalty-free alternatives to the MPEG standards. You'll find OGV files on older Wikipedia articles, in some open-source media libraries, and in the exports from a few Linux video tools. They play in Firefox and Chrome, and refuse to play basically everywhere else - Safari, iOS, Windows Media Player, most smart TVs. Wave decodes the Theora and Vorbis and re-encodes into modern H.264 and AAC inside an MP4, so the same content plays on every current 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.
The Xiph.Org Foundation released Theora in 2004 from an On2 VP3 codebase they had bought and open-sourced. Around 2010, when the HTML5 <video> element was being standardized, Theora was briefly the leading candidate as the royalty-free baseline codec - Firefox shipped a Theora decoder, and Wikipedia standardized its video library on Ogg Theora. Then Google open-sourced VP8 in the same year, and the industry moved to WebM instead. Theora files stopped being produced but the archive persists.
The performance ceiling on Theora is well below H.264 - roughly comparable to MPEG-4 Part 2 at the same bitrate, notably worse than H.264 at the same quality. In practice this means an OGV-to-MP4 conversion actually shrinks the file at the same visual quality, because the H.264 encoder makes better use of the same bit budget. A 100 MB OGV typically becomes a 60-80 MB MP4 at visually-identical quality.
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.
The audio comes through but the video is missing. Why?
The .ogv might actually be an audio-only Ogg Vorbis file with the wrong extension - some old download tools mislabelled .ogg as .ogv. Wave requires a video track and rejects audio-only sources; if you have a Vorbis audio file, it needs a dedicated audio-conversion tool.
How is OGV different from OGM?
OGM was an early-2000s hack that put non-Xiph codecs (Xvid, DivX, MP3, AC-3) into an Ogg container. It was popular briefly for anime encodes before MKV took over. Wave handles OGM through the same path as OGV - inspect first, decode whatever is inside, re-encode to H.264 + AAC.
Wikipedia video is playable now. Do I still need to convert?
For playing in-browser on Wikipedia, no - Wikipedia added WebM and MP4 alternatives to most of its video library. For a downloaded .ogv file you want to share on WhatsApp, use in a video editor, or play on iOS, converting to MP4 is still the right move.