The QuickTime File Format Specification states the following:
"Depth: A 16-bit integer that indicates the pixel depth of the compressed image. Values of 1, 2, 4, 8 ,16, 24, and 32 indicate the depth of color images. The value 32 should be used only if the image contains an alpha channel. Values of 34, 36, and 40 indicate 2-, 4-, and 8-bit grayscale, respectively, for grayscale images." There is no mention of value 33, i.e. 1-bit video (0x01) with the greyscale bit (0x20) set. I therefore suggest that we ignore the greyscale bit when processing 1-bit video. Another reason to do this is that the sample file below will be displayed properly with blue colors in QuickTime in Windows or Mac *in spite of* the greyscale bit being set. Sample file: https://drive.google.com/open?id=0B3_pEBoLs0faTThSek1EeXQ0ZHM Mats -- Mats Peterson http://matsp888.no-ip.org/~mats/
>From 60798a04ef1204dadf5395cbf7205ea3957fafbb Mon Sep 17 00:00:00 2001 From: Mats Peterson <matsp...@yahoo.com> Date: Wed, 30 Dec 2015 07:47:54 +0100 Subject: [PATCH] lavf/qtpalette: Ignore greyscale bit in 1-bit video The QuickTime File Format Specification states the following: "Depth: A 16-bit integer that indicates the pixel depth of the compressed image. Values of 1, 2, 4, 8 ,16, 24, and 32 indicate the depth of color images. The value 32 should be used only if the image contains an alpha channel. Values of 34, 36, and 40 indicate 2-, 4-, and 8-bit grayscale, respectively, for grayscale images." There is no mention of value 33, i.e. 1-bit video (0x01) with the greyscale bit (0x20) set. I therefore suggest that we ignore the greyscale bit when processing 1-bit video. Another reason to do this is that the sample file below will be displayed properly with blue colors in QuickTime in Windows or Mac *in spite of* the greyscale bit being set. Sample file: https://drive.google.com/open?id=0B3_pEBoLs0faTThSek1EeXQ0ZHM Mats --- libavformat/qtpalette.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/libavformat/qtpalette.c b/libavformat/qtpalette.c index 6544a55..0555605 100644 --- a/libavformat/qtpalette.c +++ b/libavformat/qtpalette.c @@ -51,7 +51,7 @@ int ff_get_qtpalette(int codec_id, AVIOContext *pb, uint32_t *palette) int color_count, color_start, color_end; uint32_t a, r, g, b; - if (greyscale) { + if (greyscale && bit_depth > 1) { int color_index, color_dec; /* compute the greyscale palette */ color_count = 1 << bit_depth; -- 1.7.10.4
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