Support filters and decoders that dont support negative linesizes.

This patch is based on work by stefano.

Originally committed as revision 26108 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffplay.c

@@ -1616,6 +1616,9 @@ static int input_get_buffer(AVCodecContext *codec, AVFrame *pic)
     int i, w, h, stride[4];
     unsigned edge;
 
+    if (codec->codec->capabilities & CODEC_CAP_NEG_LINESIZES)
+        perms |= AV_PERM_NEG_LINESIZES;
+
     if(pic->buffer_hints & FF_BUFFER_HINTS_VALID) {
         if(pic->buffer_hints & FF_BUFFER_HINTS_READABLE) perms |= AV_PERM_READ;
         if(pic->buffer_hints & FF_BUFFER_HINTS_PRESERVE) perms |= AV_PERM_PRESERVE;

libavfilter/avfilter.c

@@ -197,12 +197,13 @@ int avfilter_config_links(AVFilterContext *filter)
 
 char *ff_get_ref_perms_string(char *buf, size_t buf_size, int perms)
 {
-    snprintf(buf, buf_size, "%s%s%s%s%s",
+    snprintf(buf, buf_size, "%s%s%s%s%s%s",
              perms & AV_PERM_READ      ? "r" : "",
              perms & AV_PERM_WRITE     ? "w" : "",
              perms & AV_PERM_PRESERVE  ? "p" : "",
              perms & AV_PERM_REUSE     ? "u" : "",
-             perms & AV_PERM_REUSE2    ? "U" : "");
+             perms & AV_PERM_REUSE2    ? "U" : "",
+             perms & AV_PERM_NEG_LINESIZES ? "n" : "");
     return buf;
 }
 
@@ -360,15 +361,17 @@ void avfilter_start_frame(AVFilterLink *link, AVFilterBufferRef *picref)
 {
     void (*start_frame)(AVFilterLink *, AVFilterBufferRef *);
     AVFilterPad *dst = link->dstpad;
+    int perms = picref->perms;
 
     FF_DPRINTF_START(NULL, start_frame); ff_dprintf_link(NULL, link, 0); dprintf(NULL, " "); ff_dprintf_ref(NULL, picref, 1);
 
     if (!(start_frame = dst->start_frame))
         start_frame = avfilter_default_start_frame;
 
+    if (picref->linesize[0] < 0)
+        perms |= AV_PERM_NEG_LINESIZES;
     /* prepare to copy the picture if it has insufficient permissions */
-    if ((dst->min_perms & picref->perms) != dst->min_perms ||
-         dst->rej_perms & picref->perms) {
+    if ((dst->min_perms & perms) != dst->min_perms || dst->rej_perms & perms) {
         av_log(link->dst, AV_LOG_DEBUG,
                 "frame copy needed (have perms %x, need %x, reject %x)\n",
                 picref->perms,

libavfilter/avfilter.h

@@ -87,6 +87,7 @@ typedef struct AVFilterBuffer {
 #define AV_PERM_PRESERVE 0x04   ///< nobody else can overwrite the buffer
 #define AV_PERM_REUSE    0x08   ///< can output the buffer multiple times, with the same contents each time
 #define AV_PERM_REUSE2   0x10   ///< can output the buffer multiple times, modified each time
+#define AV_PERM_NEG_LINESIZES 0x20  ///< the buffer requested can have negative linesizes
 
 /**
  * Audio specific properties in a reference to an AVFilterBuffer. Since

libavfilter/vf_vflip.c

@@ -43,11 +43,13 @@ static AVFilterBufferRef *get_video_buffer(AVFilterLink *link, int perms,
                                         int w, int h)
 {
     FlipContext *flip = link->dst->priv;
+    AVFilterBufferRef *picref;
     int i;
 
-    AVFilterBufferRef *picref = avfilter_get_video_buffer(link->dst->outputs[0],
-                                                       perms, w, h);
+    if (!(perms & AV_PERM_NEG_LINESIZES))
+        return avfilter_default_get_video_buffer(link, perms, w, h);
 
+    picref = avfilter_get_video_buffer(link->dst->outputs[0], perms, w, h);
     for (i = 0; i < 4; i ++) {
         int vsub = i == 1 || i == 2 ? flip->vsub : 0;