Test cases

163 verified test files: 52 edge cases that break real players, and 111 baseline files across the codec and container grid. Each comes with a fact sheet.

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Edge cases

18 of the 52 are described here. The rest, and how each one is built, come with a token.

Orientation and aspect 6 cases
Timing and sync 9 cases
Frame rate and frames 5 cases
Colour and pixel formats 10 cases
Audio formats and channels 13 cases
Subtitles 4 cases
Structure and seeking 5 cases

Orientation and aspect 2 of 6

Anamorphic videoMP4The pixel aspect is ignored and the picture is shown squeezed: everyone looks thin.
Portrait video rotated by the display matrixMP4Players that ignore the flag show the video sideways, or squeezed into the wrong aspect.

Timing and sync 4 of 9

Audio that starts after the videoMP4The delay is dropped and the sound plays early, out of sync with the picture.
Opus in Matroska audioMatroska audioThe delay is ignored: the start is cut, or the timing is a few milliseconds off.
MPEG-TS timestamps wrapping aroundMPEG-TSPlayback freezes, jumps or stops at the wrap, and the duration comes out wrong.
MPEG-TS that doesn't start at zeroMPEG-TSThe duration shows as zero or nonsense, and the seek bar is unusable.

Frame rate and frames 3 of 5

Low frame rate videoMP4Frames are dropped, stretched or shown late, and the last one goes missing.
One picture for the whole videoMP4Nothing is shown, the duration is wrong, or seeking fails.
Variable frame rate screen recordingMP4Frames are dropped or held where the rate changes, and audio and video drift apart.

Colour and pixel formats 4 of 10

HDR10 AV1MatroskaThe HDR tags are ignored: washed-out, flat colours, or no tone mapping on an SDR screen.
Uncompressed RGB video in AVIAVIRare in modern pipelines, so it's handled badly: the picture comes out upside down, skewed, or not at all.
H.264 in RGBMP4The picture is decoded as if it were YUV: green or false colours.
HEVC 4:2:2, 10-bitMP4Many hardware decoders only handle 4:2:0: the file is refused, falls back to slow software decoding, or shows wrong colours.

Audio formats and channels 2 of 13

5.1 OpusOggMultichannel Opus is refused, downmixed, or sent to the wrong speakers.
7.1 WAVWAVThe speaker map is ignored: channels play from the wrong speakers.

Subtitles 2 of 4

Forced subtitles that aren't the default trackMatroskaForced subtitles should show anyway; many players show none.
MP4 subtitles in Chinese, Japanese and KoreanMP4Garbled characters, missing glyphs, or no subtitles at all.

Structure and seeking 1 of 5

Matroska without an indexMatroskaThe duration shows as zero, and seeking is slow or impossible.

Baseline files

The grid every player should handle. Fact sheets and recipes are public.

Video codecs17 files
The video codecs and containers most pipelines meet: H.264, HEVC, AV1, VP8, VP9 and ProRes, in MP4, MOV, Matroska and WebM. When one of these fails, the problem is basic support.
Audio codecs18 files
Common audio codecs next to the same H.264 or VP9 video, and files with no audio track at all, which some players treat as broken.
Audio-only files7 files
Audio-only files in their usual containers: M4A, FLAC, MP3, Ogg and WAV.
Channel layouts4 files
AAC in mono, stereo, 5.1 and 7.1, next to the same video.
Sample rates13 files
16-bit PCM from 8 kHz to 192 kHz, including the 44.1 kHz family (11.025, 22.05, 88.2 and 176.4 kHz) that resamplers see less often.
Frame rates10 files
Frame rates from 23.976 to 240 fps, including the NTSC rates (23.976, 29.97 and 59.94) whose timestamps never land on round numbers.
Resolutions8 files
From 360p to 2160p, plus portrait and square video, as phones and social apps produce.
Pixel formats7 files
Bit depth, chroma subsampling and range: 10-bit H.264, HEVC and AV1, 4:2:2 and 4:4:4, full-range and BT.601 video. Wrong colours start here.
HDR2 files
HEVC with HDR10 (PQ) and HLG transfer, as phones and cameras record.
Interlaced video2 files
Interlaced H.264, top field first and bottom field first, as broadcast and camcorder material is.
Alpha channel2 files
Video with transparency: ProRes 4444 and VP9 with an alpha channel, as motion graphics use.
MP4 layout3 files
The same MP4 three ways: index first (faststart), index at the end, and fragmented. Players that stream or seek over HTTP depend on the difference.
HLS4 files
HLS with MPEG-TS and fMP4 segments, an audio-only stream, and a three-rendition bitrate ladder.
DASH1 file
DASH with fMP4 segments.
Subtitles6 files
Subtitles in the formats players meet: SRT, ASS, WebVTT and MP4 text, in the file and as sidecar files.
Tracks1 file
Two audio languages in one file, to check track selection.
Durations6 files
From 2 seconds to 30 minutes, to check duration, seeking and memory over a long file.

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