From b5ba361d8f8908ab37a104b0110910926d94d57f Mon Sep 17 00:00:00 2001 From: Gerd Hoffmann Date: Tue, 21 Jan 2020 07:02:10 +0100 Subject: Revert "vnc: allow fall back to RAW encoding" This reverts commit de3f7de7f4e257ce44cdabb90f5f17ee99624557. Remove VNC optimization to reencode framebuffer update as raw if it's smaller than the default encoding. QEMU's implementation was naive and didn't account for the ZLIB z_stream mutating with each compression. Because of the mutation, simply resetting the output buffer's offset wasn't sufficient to "rewind" the operation. The mutated z_stream would generate future zlib blocks which referred to symbols in past blocks which weren't sent. This would lead to artifacting. Considering that ZRLE is never larger than raw and even though ZLIB can occasionally be fractionally larger than raw, the overhead of implementing this optimization correctly isn't worth it. Signed-off-by: Cameron Esfahani Signed-off-by: Gerd Hoffmann (cherry picked from commit 0780ec7be82dd4781e9fd216b5d99a125882ff5a) Signed-off-by: Michael Roth --- ui/vnc.c | 20 ++------------------ 1 file changed, 2 insertions(+), 18 deletions(-) diff --git a/ui/vnc.c b/ui/vnc.c index 87b8045afe..f94b3a257e 100644 --- a/ui/vnc.c +++ b/ui/vnc.c @@ -898,8 +898,6 @@ int vnc_raw_send_framebuffer_update(VncState *vs, int x, int y, int w, int h) int vnc_send_framebuffer_update(VncState *vs, int x, int y, int w, int h) { int n = 0; - bool encode_raw = false; - size_t saved_offs = vs->output.offset; switch(vs->vnc_encoding) { case VNC_ENCODING_ZLIB: @@ -922,24 +920,10 @@ int vnc_send_framebuffer_update(VncState *vs, int x, int y, int w, int h) n = vnc_zywrle_send_framebuffer_update(vs, x, y, w, h); break; default: - encode_raw = true; + vnc_framebuffer_update(vs, x, y, w, h, VNC_ENCODING_RAW); + n = vnc_raw_send_framebuffer_update(vs, x, y, w, h); break; } - - /* If the client has the same pixel format as our internal buffer and - * a RAW encoding would need less space fall back to RAW encoding to - * save bandwidth and processing power in the client. */ - if (!encode_raw && vs->write_pixels == vnc_write_pixels_copy && - 12 + h * w * VNC_SERVER_FB_BYTES <= (vs->output.offset - saved_offs)) { - vs->output.offset = saved_offs; - encode_raw = true; - } - - if (encode_raw) { - vnc_framebuffer_update(vs, x, y, w, h, VNC_ENCODING_RAW); - n = vnc_raw_send_framebuffer_update(vs, x, y, w, h); - } - return n; } -- cgit v1.2.3