README.media (2111B)
1 Provenance of the media samples 2 =============================== 3 4 Unlike the rest of the files in this directory, the three files below 5 were not found anywhere: they are generated, and the recipe that 6 generates them is `contrib/gen_testmedia.sh' in this repository. Every 7 frame and every sample comes out of FFmpeg's synthetic `lavfi' sources 8 (a solid colour, a box, a sine wave), so there is no third party work 9 involved and nothing to attribute. They are dedicated to the public 10 domain (CC0 1.0). 11 12 They exist because the video thumbnail plugins (thumbnailffmpeg, 13 thumbnailgst) and the audio preview plugins (previewopus, previewgst) 14 need input that is long enough to seek around in, and none of the other 15 test files here is even 30 seconds long. Keeping them synthetic also 16 keeps them small: all three together are smaller than a single one of 17 the photographs in this directory. 18 19 Theora and Vorbis in an Ogg container were chosen because both plugin 20 backends can decode them without any additional codec package: FFmpeg has 21 both built in, and for GStreamer they live in gst-plugins-base. 22 23 thumbnail_pattern.ogv 90s, Theora, 160x120, 5fps, no audio (14K) 24 25 Solid black for the first 20 seconds, then solid red. The 26 thumbnailers sample about 30 seconds in (bounded by a third of the 27 duration, which is why the file is 90 and not 35 seconds long), so 28 a thumbnail taken from the wrong moment comes out black instead of 29 red, and test_thumbnailffmpeg/test_thumbnailgst notice. Each frame 30 also carries a small white box: the thumbnailers deliberately skip 31 perfectly flat frames, which a fade-in leader would produce, and 32 the box keeps the test from tripping over that. 33 34 preview_tone.ogg 30s, Vorbis, mono, 8kHz (21K) 35 36 A 440Hz tone for 15 seconds followed by an 880Hz tone. 8kHz mono 37 is more than enough for something that gets re-encoded at 24 kbps. 38 39 preview_tone.ogv 30s, Theora + Vorbis (28K) 40 41 The same audio in a file that also carries video, so that the 42 preview plugins are exercised on a video container as well.