Convert FLV to MP4
FLV is Adobe's Flash Video container - dead as a platform but still sitting in old archives. Many FLVs carry H.264 video and AAC audio, which means Wave can repackage without re-encoding. Others use older codecs and need a light transcode.
What actually changes
Flash Video files come in two eras: pre-2008 FLVs use Sorenson Spark or VP6 video with MP3 or Speex audio, and post-2008 FLVs typically use H.264 with AAC. Wave inspects the streams and picks its path automatically.
When the source is H.264 + AAC (most common for FLVs from 2010 onward), the conversion is a re-mux: streams copied bit-for-bit into MP4, with a fast-start rewrite. When it's a pre-2008 codec, the video re-encodes to MPEG-4 Part 2 and audio to AAC. Both paths run locally in the browser.
Three steps.
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Step 1
Drop the FLV onto the card.
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Step 2
Wave shows either Fast copy (H.264 source) or Re-encode needed (older codec).
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Step 3
Convert and save the MP4.
Answers, specifically.
Why bother converting FLV?
Because Flash is gone. No modern browser plays FLV, no phone plays FLV, no video editor imports FLV cleanly. MP4 is the universal replacement.
Will the fast-copy version be identical to the FLV?
Yes. If the FLV's streams are already MP4-compatible, the streams are copied without touching any pixels or samples.
Some of my FLVs are very old - will they still convert?
Usually. Wave supports Sorenson Spark and VP6 through re-encode. Some very old FLVs with corrupted headers may fail during inspect - try re-downloading if you can.
How big can the FLV be?
About 1.5 GB in-browser. FLVs from the era rarely approach this ceiling.
Does the aspect ratio survive?
Yes. Wave preserves the source's stored aspect ratio in the MP4 metadata, including anamorphic cases.