Depends on resolution and PNG codec. A 1080p PNG frame is typically 2 to 5 MB; a 1080p JPG at quality-85 is 200 to 500 KB; a 4K PNG is 6 to 15 MB. At the extreme, every-frame PNG extraction of a 10-minute 1080p WebM produces ~50 GB total.
Frame extraction is fast — typically 20 to 30% of source duration on the standard pipeline. A 5-minute WebM → PNG bundle finishes in about a minute regardless of frame count, because the bottleneck is the PNG encoder, not the WebM demuxer.
Yes, subject to whatever licence governs the source WebM content. The format change adds no claim — we add no watermark and assert no licence over the PNG output. Copyright tracks the source, not the converter.
