Define the visible problem
Interlaced source material can show comb-like motion artefacts when displayed without appropriate treatment. First identify a repeatable moment with movement in media you own. Record the file, time, player version and display arrangement. A still frame without motion is a weak basis for judging a temporal processing choice.
Keep the original file unchanged. This guide concerns player-side review, not converting a collection or promising that one deinterlacer improves every source. Before changing anything, list existing filters and whether the material is believed to be interlaced or progressive, including the basis for that belief.
Make one deinterlacing comparison
The documented --deinterlace choices are yes, no and auto, with no the default. Automatic detection can be wrong. Compare the relevant modes on the same moving passage, keeping other playback settings constant. Inspect both the affected edges and the overall movement rather than judging a single paused image.
If a progressive sample looks worse after forcing deinterlacing, treat that as a reason to review the assumption, not as proof that the original file is damaged. Likewise, an interlaced flag in metadata is useful evidence but not a universal quality guarantee. Keep separate notes for source properties and the visual result you actually observe locally.
Avoid stacked processing ambiguity
Inspect the configured filter chain before adding another deinterlacing stage. Multiple overlapping treatments can make the result difficult to interpret. Change one setting and preserve the baseline so an improvement or regression has a traceable cause.
Check the documentation for the installed output path when interpreting behaviour; deinterlacing implementation and hardware interactions can depend on configuration. Do not turn a successful sample into a claim about every GPU or codec. No hardware or motion comparison was performed for this guide, so the proposed observations remain work for the local installation.
Keep the next file independent
mpv can retain changed settings across playlist items unless you specify an appropriate reset policy. After reviewing the interlaced sample, open a known progressive sample and inspect the active state. Decide whether the deinterlacing choice belongs to one file, a named task or a broader configuration.
Record the final decision with the source and version, and preserve a route back to the baseline. If the requirement is a new progressive master file, use a documented conversion workflow and validate that output separately. A player-side viewing choice does not rewrite the original, establish archival quality or certify that another device will produce the same result.
Questions answered
Is automatic interlace detection always correct?
No. The developer documentation warns that detection or flags can be wrong; compare a representative moving passage.
Does changing playback deinterlacing create a new progressive file?
No. A player-side setting is separate from an encoding or export workflow.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.