lavc: add an option for exporting cropping information to the caller

Also, add generic code for handling cropping, so the decoders can export
just the cropping size and not bother with the rest.

1 files changed, 116 insertions, 1 deletions

diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index 0fd41ab482..f4088cdae8 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -29,6 +29,7 @@
 #include "libavutil/frame.h"
 #include "libavutil/hwcontext.h"
 #include "libavutil/imgutils.h"
+#include "libavutil/intmath.h"
 
 #include "avcodec.h"
 #include "bytestream.h"
@@ -450,6 +451,111 @@ int attribute_align_arg avcodec_send_packet(AVCodecContext *avctx, const AVPacke
     return 0;
 }
 
+static int calc_cropping_offsets(size_t offsets[4], const AVFrame *frame,
+                                 const AVPixFmtDescriptor *desc)
+{
+    int i, j;
+
+    for (i = 0; frame->data[i]; i++) {
+        const AVComponentDescriptor *comp = NULL;
+        int shift_x = (i == 1 || i == 2) ? desc->log2_chroma_w : 0;
+        int shift_y = (i == 1 || i == 2) ? desc->log2_chroma_h : 0;
+
+        if (desc->flags & (AV_PIX_FMT_FLAG_PAL | AV_PIX_FMT_FLAG_PSEUDOPAL) && i == 1) {
+            offsets[i] = 0;
+            break;
+        }
+
+        /* find any component descriptor for this plane */
+        for (j = 0; j < desc->nb_components; j++) {
+            if (desc->comp[j].plane == i) {
+                comp = &desc->comp[j];
+                break;
+            }
+        }
+        if (!comp)
+            return AVERROR_BUG;
+
+        offsets[i] = (frame->crop_top  >> shift_y) * frame->linesize[i] +
+                     (frame->crop_left >> shift_x) * comp->step;
+    }
+
+    return 0;
+}
+
+static int apply_cropping(AVCodecContext *avctx, AVFrame *frame)
+{
+    const AVPixFmtDescriptor *desc;
+    size_t offsets[4];
+    int i;
+
+    /* make sure we are noisy about decoders returning invalid cropping data */
+    if (frame->crop_left >= INT_MAX - frame->crop_right        ||
+        frame->crop_top  >= INT_MAX - frame->crop_bottom       ||
+        (frame->crop_left + frame->crop_right) >= frame->width ||
+        (frame->crop_top + frame->crop_bottom) >= frame->height) {
+        av_log(avctx, AV_LOG_WARNING,
+               "Invalid cropping information set by a decoder: %zu/%zu/%zu/%zu "
+               "(frame size %dx%d). This is a bug, please report it\n",
+               frame->crop_left, frame->crop_right, frame->crop_top, frame->crop_bottom,
+               frame->width, frame->height);
+        frame->crop_left   = 0;
+        frame->crop_right  = 0;
+        frame->crop_top    = 0;
+        frame->crop_bottom = 0;
+        return 0;
+    }
+
+    if (!avctx->apply_cropping)
+        return 0;
+
+    desc = av_pix_fmt_desc_get(frame->format);
+    if (!desc)
+        return AVERROR_BUG;
+
+    /* Apply just the right/bottom cropping for hwaccel formats. Bitstream
+     * formats cannot be easily handled here either (and corresponding decoders
+     * should not export any cropping anyway), so do the same for those as well.
+     * */
+    if (desc->flags & (AV_PIX_FMT_FLAG_BITSTREAM | AV_PIX_FMT_FLAG_HWACCEL)) {
+        frame->width      -= frame->crop_right;
+        frame->height     -= frame->crop_bottom;
+        frame->crop_right  = 0;
+        frame->crop_bottom = 0;
+        return 0;
+    }
+
+    /* calculate the offsets for each plane */
+    calc_cropping_offsets(offsets, frame, desc);
+
+    /* adjust the offsets to avoid breaking alignment */
+    if (!(avctx->flags & AV_CODEC_FLAG_UNALIGNED)) {
+        int min_log2_align = INT_MAX;
+
+        for (i = 0; frame->data[i]; i++) {
+            int log2_align = offsets[i] ? av_ctz(offsets[i]) : INT_MAX;
+            min_log2_align = FFMIN(log2_align, min_log2_align);
+        }
+
+        if (min_log2_align < 5) {
+            frame->crop_left &= ~((1 << min_log2_align) - 1);
+            calc_cropping_offsets(offsets, frame, desc);
+        }
+    }
+
+    for (i = 0; frame->data[i]; i++)
+        frame->data[i] += offsets[i];
+
+    frame->width      -= (frame->crop_left + frame->crop_right);
+    frame->height     -= (frame->crop_top  + frame->crop_bottom);
+    frame->crop_left   = 0;
+    frame->crop_right  = 0;
+    frame->crop_top    = 0;
+    frame->crop_bottom = 0;
+
+    return 0;
+}
+
 int attribute_align_arg avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
 {
     AVCodecInternal *avci = avctx->internal;
@@ -472,6 +578,14 @@ int attribute_align_arg avcodec_receive_frame(AVCodecContext *avctx, AVFrame *fr
             return ret;
     }
 
+    if (avctx->codec_type == AVMEDIA_TYPE_VIDEO) {
+        ret = apply_cropping(avctx, frame);
+        if (ret < 0) {
+            av_frame_unref(frame);
+            return ret;
+        }
+    }
+
     avctx->frame_number++;
 
     return 0;
@@ -1029,7 +1143,8 @@ int ff_get_buffer(AVCodecContext *avctx, AVFrame *frame, int flags)
     ret = avctx->get_buffer2(avctx, frame, flags);
 
 end:
-    if (avctx->codec_type == AVMEDIA_TYPE_VIDEO && !override_dimensions) {
+    if (avctx->codec_type == AVMEDIA_TYPE_VIDEO && !override_dimensions &&
+        !(avctx->codec->caps_internal & FF_CODEC_CAP_EXPORTS_CROPPING)) {
         frame->width  = avctx->width;
         frame->height = avctx->height;
     }