avcodec/avrndec: Fix cropping

This also switches to using a separate AVCodecContext for the inner mjpeg decoder
which is cleaner and avoids fields from being overwritten with wrong values

Fixes Ticket162
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/avrndec.c

@@ -26,7 +26,7 @@
 #include "libavutil/imgutils.h"
 
 typedef struct {
-    MJpegDecodeContext mjpeg_ctx;
+    AVCodecContext *mjpeg_avctx;
     int is_mjpeg;
     int interlace; //FIXME use frame.interlaced_frame
     int tff;
@@ -45,8 +45,31 @@ static av_cold int init(AVCodecContext *avctx)
         return AVERROR(EINVAL);
     }
 
-    if(a->is_mjpeg)
-        return ff_mjpeg_decode_init(avctx);
+    if(a->is_mjpeg) {
+        AVCodec *codec = avcodec_find_decoder(AV_CODEC_ID_MJPEG);
+        AVDictionary *thread_opt = NULL;
+        if (!codec) {
+            av_log(avctx, AV_LOG_ERROR, "MJPEG codec not found\n");
+            return AVERROR_DECODER_NOT_FOUND;
+        }
+
+        a->mjpeg_avctx = avcodec_alloc_context3(codec);
+
+        av_dict_set(&thread_opt, "threads", "1", 0); // Is this needed ?
+        a->mjpeg_avctx->refcounted_frames = 1;
+        a->mjpeg_avctx->flags = avctx->flags;
+        a->mjpeg_avctx->idct_algo = avctx->idct_algo;
+        a->mjpeg_avctx->lowres = avctx->lowres;
+        a->mjpeg_avctx->width = avctx->width;
+        a->mjpeg_avctx->height = avctx->height;
+
+        if ((ret = ff_codec_open2_recursive(a->mjpeg_avctx, codec, &thread_opt)) < 0) {
+            av_log(avctx, AV_LOG_ERROR, "MJPEG codec failed to open\n");
+        }
+        av_dict_free(&thread_opt);
+
+        return ret;
+    }
 
     if ((ret = av_image_check_size(avctx->width, avctx->height, 0, avctx)) < 0)
         return ret;
@@ -68,8 +91,8 @@ static av_cold int end(AVCodecContext *avctx)
 {
     AVRnContext *a = avctx->priv_data;
 
-    if(a->is_mjpeg)
-        ff_mjpeg_decode_end(avctx);
+    avcodec_close(a->mjpeg_avctx);
+    av_freep(&a->mjpeg_avctx);
 
     return 0;
 }
@@ -83,8 +106,27 @@ static int decode_frame(AVCodecContext *avctx, void *data,
     int buf_size       = avpkt->size;
     int y, ret, true_height;
 
-    if(a->is_mjpeg)
-        return ff_mjpeg_decode_frame(avctx, data, got_frame, avpkt);
+    if(a->is_mjpeg) {
+        ret = avcodec_decode_video2(a->mjpeg_avctx, data, got_frame, avpkt);
+
+        if (ret >= 0 && *got_frame && avctx->width <= p->width && avctx->height <= p->height) {
+            int shift = p->height - avctx->height;
+            int subsample_h, subsample_v;
+
+            av_pix_fmt_get_chroma_sub_sample(avctx->pix_fmt, &subsample_h, &subsample_v);
+
+            p->data[0] += p->linesize[0] * shift;
+            if (p->data[2]) {
+                p->data[1] += p->linesize[1] * (shift>>subsample_v);
+                p->data[2] += p->linesize[2] * (shift>>subsample_v);
+            }
+
+            p->width  = avctx->width;
+            p->height = avctx->height;
+        }
+        avctx->pix_fmt = a->mjpeg_avctx->pix_fmt;
+        return ret;
+    }
 
     true_height    = buf_size / (2*avctx->width);