[FFmpeg-devel,PATCHv3] add signature filter for MPEG7 video signature

diff --git a/libavfilter/signature.h b/libavfilter/signature.h
index ed1c32e..195c94c 100644
--- a/libavfilter/signature.h
+++ b/libavfilter/signature.h
@@ -120,6 +120,8 @@  typedef struct {
     int coursecount; /* counter from 0 to 89 */
     int midcourse;   /* whether it is a coursesignature beginning from 45 + i * 90 */
     uint32_t lastindex; /* helper to store amount of frames */
+
+    int exported; /* boolean whether stream already exported */
 } StreamContext;
 
 typedef struct {
diff --git a/libavfilter/vf_signature.c b/libavfilter/vf_signature.c
index 2b51724..e1fff9b 100644
--- a/libavfilter/vf_signature.c
+++ b/libavfilter/vf_signature.c
@@ -71,6 +71,7 @@  AVFILTER_DEFINE_CLASS(signature);
 
 static int query_formats(AVFilterContext *ctx)
 {
+    /* all formats with a seperate gray value */
     static const enum AVPixelFormat pix_fmts[] = {
         AV_PIX_FMT_GRAY8,
         AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV411P,
@@ -586,21 +587,56 @@  static int export(AVFilterContext *ctx, StreamContext *sc, int input)
 static int request_frame(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
-    SignatureContext *sc = ctx->priv;
-    int i, ret;
+    SignatureContext *sic = ctx->priv;
+    StreamContext *sc, *sc2;
+    MatchingInfo match;
+    int i, j, ret;
+    int lookup = 1; /* indicates wheather EOF of all files is reached */
+
+    /* process all inputs */
+    for (i = 0; i < sic->nb_inputs; i++){
+        sc = &(sic->streamcontexts[i]);
 
-    for (i = 0; i < sc->nb_inputs; i++){
         ret = ff_request_frame(ctx->inputs[i]);
-        // TODO handle this in a better way?
-        // Problem is the following:
-        // Assuming two inputs, inputA with 50 frames, inputB with 100 frames
-        // simply returning ret when < 0 would result in not filtering inputB
-        // after 50 frames anymore, not wanted
-        // only returning ret at the end would result in only respecting the error
-        // values of the last input, please comment
+
+        /* return if unexspected error occurs in input stream */
         if (ret < 0 && ret != AVERROR_EOF)
             return ret;
+
+        /* export signature at EOF */
+        if (ret == AVERROR_EOF){
+            /* export if wanted */
+            if (strlen(sic->filename) > 0) {
+                if (export(ctx, sc, i) < 0)
+                    return ret;
+            }
+            sc->exported = 1;
+        }
+        lookup &= sc->exported;
+    }
+
+    /* signature lookup */
+    if (lookup && sic->mode != MODE_OFF) {
+        /* iterate over every pair */
+        for (i = 0; i < sic->nb_inputs; i++) {
+            sc = &(sic->streamcontexts[i]);
+            for (j = i+1; j < sic->nb_inputs; j++) {
+                sc2 = &(sic->streamcontexts[j]);
+                match = lookup_signatures(ctx, sic, sc, sc2, sic->mode);
+                if (match.score != 0) {
+                    av_log(ctx, AV_LOG_INFO, "matching of video %d at %f and %d at %f, %d frames matching\n",
+                            i, ((double) match.first->pts * sc->time_base.num) / sc->time_base.den,
+                            j, ((double) match.second->pts * sc2->time_base.num) / sc2->time_base.den,
+                            match.matchframes);
+                    if (match.whole)
+                        av_log(ctx, AV_LOG_INFO, "whole video matching\n");
+                } else {
+                    av_log(ctx, AV_LOG_INFO, "no matching of video %d and %d\n", i, j);
+                }
+            }
+        }
     }
+
     return ret;
 }
 
@@ -663,52 +699,14 @@  static av_cold int init(AVFilterContext *ctx)
 static av_cold void uninit(AVFilterContext *ctx)
 {
     SignatureContext *sic = ctx->priv;
-    StreamContext *sc, *sc2;
+    StreamContext *sc;
     void* tmp;
     FineSignature* finsig;
     CourseSignature* cousig;
-    MatchingInfo match;
-    int i,j;
-
-    //TODO export and especially lookup_signature can have a return value to show some error etc.
-    //How could this be handled in this function?
+    int i;
 
-    /* signature export */
-    if (strlen(sic->filename) > 0) {
-        for (i = 0; i < sic->nb_inputs; i++) {
-            /* if filter frame was called at least once */
-            if (&(sic->streamcontexts[i]) && (&(sic->streamcontexts[i]))->curfinesig)
-                export(ctx, &(sic->streamcontexts[i]), i);
-        }
-    }
-
-    /* signature lookup */
-    if (sic->mode != MODE_OFF) {
-        /* iterate over every pair */
-        for (i = 0; i < sic->nb_inputs; i++) {
-            sc = &(sic->streamcontexts[i]);
-            if (sc && sc->curfinesig) {
-                for (j = i+1; j < sic->nb_inputs; j++) {
-                    sc2 = &(sic->streamcontexts[j]);
-                    if (sc2 && sc2->curfinesig) {
-                        match = lookup_signatures(ctx, sic, sc, sc2, sic->mode);
-                        if (match.score != 0) {
-                            av_log(ctx, AV_LOG_INFO, "matching of video %d at %f and %d at %f, %d frames matching\n",
-                                    i, ((double) match.first->pts * sc->time_base.num) / sc->time_base.den,
-                                    j, ((double) match.second->pts * sc2->time_base.num) / sc2->time_base.den,
-                                    match.matchframes);
-                            if (match.whole)
-                                av_log(ctx, AV_LOG_INFO, "whole video matching\n");
-                        } else {
-                            av_log(ctx, AV_LOG_INFO, "no matching of video %d and %d\n", i, j);
-                        }
-                    }
-                }
-            }
-        }
-    }
 
-    /* cleanup */
+    /* free the lists */
     if (sic->streamcontexts != NULL) {
         for (i = 0; i < sic->nb_inputs; i++) {
             sc = &(sic->streamcontexts[i]);