Sony XAVC S clips on a Mac: why Finder shows them and Preview will not

Sony cameras record XAVC S, the files end in .MP4, and the Mac ought to open them without ceremony. Sometimes it does not: Preview refuses, QuickTime stutters, or an editor imports the clip and shows nothing.

XAVC S is not an exotic format. It is H.264 or HEVC inside an MP4 container, recorded at high bitrate. Knowing that narrows the possible causes to three.

Find out what the clip actually contains

ffprobe -v error -select_streams v:0 \
  -show_entries stream=codec_name,profile,level,width,height,r_frame_rate,bit_rate,pix_fmt \
  -of default=noprint_wrappers=1 C0001.MP4

Three fields decide everything.

codec_name will be h264 or hevc. Both are widely supported, so this is rarely the problem on its own.

pix_fmt is where trouble starts. yuv420p is 8-bit and universally handled. yuv422p10le is 10-bit 4:2:2, which XAVC S-I and the higher-quality modes use, and which many players and older editors will not decode.

bit_rate is the other. XAVC S can record at several hundred megabits per second in its intra-frame modes. That is a great deal of data per second to pull off a disk and decode in real time, and a machine that manages 4K HEVC at 100 Mbps may fall over at 600.

The 4:2:2 10-bit problem

If pix_fmt shows 10-bit 4:2:2, that is almost certainly your answer. It is a professional acquisition format, and support outside professional tools is patchy.

For playback, convert a viewing copy:

ffmpeg -i C0001.MP4 -c:v libx264 -crf 20 -preset medium \
  -pix_fmt yuv420p -c:a aac -b:a 192k C0001_view.mp4

-pix_fmt yuv420p is the important flag. It converts to 8-bit 4:2:0, which everything opens.

Do this for viewing and sharing, not for grading. The extra colour information in 4:2:2 10-bit is the reason to shoot it, and converting throws that away. Keep the original.

For editing, make proxies and relink to the originals at export:

ffmpeg -i C0001.MP4 -vf scale=1280:-2 -c:v libx264 -preset veryfast \
  -crf 23 -c:a aac -b:a 128k C0001_proxy.mp4

Manatee performs the same conversions on the Mac without a command line and without uploading footage, working from a duplicate so the camera original is left alone.

The incomplete card copy

This one catches people who drag clips out of the card’s folders rather than copying the card whole.

Sony cameras write a structured directory: clips in one place, and metadata, proxies and index files in others. Some applications read that structure and refuse a clip lifted out of it, even though the clip itself is intact and plays fine elsewhere.

Copy the entire card, preserving the folder layout, and import from that copy. If you already have loose clips, they will usually play in a general-purpose player even when a professional editor rejects them, which is a useful way to confirm the file is fine and the structure is what is missing.

When it is genuinely damaged

If ffprobe reports no duration or errors out, the file is damaged rather than unsupported.

ffprobe -v error -show_entries format=duration,size -of default=noprint_wrappers=1 C0001.MP4

The usual cause is an interrupted recording: battery exhaustion, or a card removed while writing. An MP4’s index is written last, after the frame data, because it cannot be completed until recording stops. A healthy file is laid out like this:

ftyp → free → mdat (the video data) → moov (the index)

Interrupt it and every frame is present with nothing to map them. Manatee rebuilds the index from what survives and writes a clean copy from a duplicate, so the original is untouched by the attempt. How to check whether a video file is corrupted is the quick test, and why some videos play on iPhone but not on Mac covers the related case where support rather than damage is the issue.

Cards and reliability

High-bitrate recording is demanding on cards, and a card that cannot sustain the write rate produces dropped frames or truncated clips rather than a clear error.

Use cards rated for the bitrate you are recording. Format them in the camera rather than on the Mac. Copy the whole card before reviewing, and verify the copy for anything that matters, using the method in verifying a file arrived intact.

Questions

The clip plays in one application and not another. That is a support difference, not damage. Check pix_fmt; 10-bit 4:2:2 is the usual dividing line between tools that open it and tools that do not.

Why is the file so large for its length? XAVC S intra-frame modes store every frame independently, which makes editing responsive and storage expensive. That is the trade the format makes deliberately.

Can I convert without losing quality? Not entirely; any re-encode discards something. At a high quality setting the loss is not visible, but keep the original for anything you will grade or archive.

Preview shows a thumbnail but will not play it. Thumbnails come from a single decoded frame, which is much cheaper than sustained playback. A thumbnail proves the file is readable, not that your Mac can decode it in real time.