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mpv/video/sws_utils.h
wm4 083adf97e1 sws_utils: work around libswscale corrupting memory yet again
If the alignment is less than 16, certain libswscale code paths will
silently corrupt memory outside of the target buffer. This actually
affected the libmpv software rendering API (that was fun to debug).
Rather than passing this problem to the next API user, try to avoid it
within libmpv.

It's unclear which alignment libswscale requires for safe operation. I'm
picking 32 (one more than the observed safe value in the case I
experienced), because libavfilter mostly uses this value.

The way to work this around is slow: just make a full copy of the entire
input or output image. Possibly this could be optimized by using the
slice API, but that would be more effort, and would likely expose
further libswscale bugs. Hope that this is a rarely needed path.

The next commit will update the alignment requirement documentation
bits.
2020-09-17 15:24:27 +02:00

83 lines
2.6 KiB
C

#ifndef MPLAYER_SWS_UTILS_H
#define MPLAYER_SWS_UTILS_H
#include <stdbool.h>
#include "mp_image.h"
struct mp_image;
struct mpv_global;
// libswscale currently requires 16 bytes alignment for row pointers and
// strides. Otherwise, it will print warnings and use slow codepaths.
// Guaranteed to be a power of 2 and > 1.
#define SWS_MIN_BYTE_ALIGN MP_IMAGE_BYTE_ALIGN
extern const int mp_sws_fast_flags;
bool mp_sws_supported_format(int imgfmt);
int mp_image_swscale(struct mp_image *dst, struct mp_image *src,
int my_sws_flags);
int mp_image_sw_blur_scale(struct mp_image *dst, struct mp_image *src,
float gblur);
enum mp_sws_scaler {
MP_SWS_AUTO = 0, // use command line
MP_SWS_SWS,
MP_SWS_ZIMG,
};
struct mp_sws_context {
// Can be set for verbose error printing.
struct mp_log *log;
// User configuration. These can be changed freely, at any time.
// mp_sws_scale() will handle the changes transparently.
int flags;
bool allow_zimg; // use zimg if available (ignores filters and all)
bool force_reload;
// These are also implicitly set by mp_sws_scale(), and thus optional.
// Setting them before that call makes sense when using mp_sws_reinit().
struct mp_image_params src, dst;
// This is unfortunately a hack: bypass command line choice
enum mp_sws_scaler force_scaler;
// If zimg is used. Need to manually invalidate cache (set force_reload).
// Conflicts with enabling command line opts.
struct zimg_opts *zimg_opts;
// Changing these requires setting force_reload=true.
// By default, they are NULL.
// Freeing the mp_sws_context will deallocate these if set.
struct SwsFilter *src_filter, *dst_filter;
double params[2];
// Cached context (if any)
struct SwsContext *sws;
bool supports_csp;
// Private.
struct m_config_cache *opts_cache;
struct mp_sws_context *cached; // contains parameters for which sws is valid
struct mp_zimg_context *zimg;
bool zimg_ok;
struct mp_image *aligned_src, *aligned_dst;
};
struct mp_sws_context *mp_sws_alloc(void *talloc_ctx);
void mp_sws_enable_cmdline_opts(struct mp_sws_context *ctx, struct mpv_global *g);
int mp_sws_reinit(struct mp_sws_context *ctx);
int mp_sws_scale(struct mp_sws_context *ctx, struct mp_image *dst,
struct mp_image *src);
bool mp_sws_supports_formats(struct mp_sws_context *ctx,
int imgfmt_out, int imgfmt_in);
struct mp_image *mp_img_swap_to_native(struct mp_image *img);
#endif /* MP_SWS_UTILS_H */
// vim: ts=4 sw=4 et tw=80