From 7eb53a10e1090cd3551361d2b5bfab274d73078e Mon Sep 17 00:00:00 2001 From: sam Date: Wed, 14 Oct 2026 21:39:49 +0200 Subject: [PATCH] GIF: write a delay per image and a loop block into animations FileGIF wrote animated GIFs without a graphics control extension, so every image had a delay of 0. ffprobe saw a single image in a 50 image file and viewers raced through the rest or showed only the first one. Upstream writes the same file. An animation (FileGIF on a path, not a frame of a GIF list) is now GIF89a with a NETSCAPE2.0 block that loops forever and a delay per image. The delay follows the running time in hundredths of a second: 25 fps gives 4 each, 30 fps the pattern 3,4,3. Delays under 2 are raised to 2, since viewers slow those down. Checked: 25 fps renders 50 images of 4/100 s, ffprobe reads 50 frames at 25 fps and 2.0 s. A project with this GIF as its source renders frame 25 identical to ffmpeg's frame 25. GIF list frames are unchanged. Co-Authored-By: Claude Opus 5.5 --- cinelerra-5.1/cinelerra/filegif.C | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/cinelerra-5.1/cinelerra/filegif.C b/cinelerra-5.1/cinelerra/filegif.C index e6a54cac..0738f2aa 100644 --- a/cinelerra-5.1/cinelerra/filegif.C +++ b/cinelerra-5.1/cinelerra/filegif.C @@ -694,9 +694,40 @@ int FileGIF::write_frame(VFrame *frame) result = 1; } } +// An animation (written to a path, not a frame of a GIF list) needs GIF89a, +// a loop block and a delay per image. Without them every image had a delay +// of 0: viewers raced through it or showed the first image only. + int anim = fd >= 0; + if( !result && !writes && anim ) + EGifSetGifVersion(gif_file, true); if( !result && !writes && EGifPutScreenDesc(gif_file, w, h, depth, 0, 0) == GIF_ERROR ) result = 1; + if( !result && !writes && anim ) { +// NETSCAPE2.0 block, loop count 0: repeat forever + static const GifByteType loop[] = { 1, 0, 0 }; + if( EGifPutExtensionLeader(gif_file, APPLICATION_EXT_FUNC_CODE) == GIF_ERROR || + EGifPutExtensionBlock(gif_file, 11, "NETSCAPE2.0") == GIF_ERROR || + EGifPutExtensionBlock(gif_file, sizeof(loop), loop) == GIF_ERROR || + EGifPutExtensionTrailer(gif_file) == GIF_ERROR ) + result = 1; + } + if( !result && anim ) { +// The delay is in 1/100 s, taken from the running time: 30 fps gives 3,4,3. +// Viewers slow down delays under 2, so faster rates play at 50 fps. + double rate = asset->frame_rate > 0 ? asset->frame_rate : 10; + int delay = (int)(100 * (writes + 1) / rate + 0.5) - + (int)(100 * writes / rate + 0.5); + GraphicsControlBlock gcb; + gcb.DisposalMode = DISPOSAL_UNSPECIFIED; + gcb.UserInputFlag = false; + gcb.DelayTime = delay < 2 ? 2 : delay; + gcb.TransparentColor = NO_TRANSPARENT_COLOR; + GifByteType ext[4]; + size_t ext_len = EGifGCBToExtension(&gcb, ext); + if( EGifPutExtension(gif_file, GRAPHICS_EXT_FUNC_CODE, ext_len, ext) == GIF_ERROR ) + result = 1; + } if( !result && EGifPutImageDesc(gif_file, 0, 0, w, h, 0, cmap) == GIF_ERROR ) result = 1; -- 2.43.0