From f968ef922d5b1e1ba29145bceaa0278ece4f88e0 Mon Sep 17 00:00:00 2001
From: Philip Langdale <philipl@overt.org>
Date: Sun, 20 Mar 2011 16:29:04 -0700
Subject: CrystalHD: Refine heuristic logic.

---
 libavcodec/crystalhd.c | 57 +++++++++++++++++++++++++-------------------------
 1 file changed, 28 insertions(+), 29 deletions(-)

(limited to 'libavcodec/crystalhd.c')

diff --git a/libavcodec/crystalhd.c b/libavcodec/crystalhd.c
index 132923cd02..6e956b8037 100644
--- a/libavcodec/crystalhd.c
+++ b/libavcodec/crystalhd.c
@@ -512,8 +512,7 @@ static inline CopyRet copy_frame(AVCodecContext *avctx,
 {
     BC_STATUS ret;
     BC_DTS_STATUS decoder_status;
-    uint8_t confirmed_interlaced;
-    uint8_t ignore_interlaced;
+    uint8_t trust_interlaced;
     uint8_t interlaced;
 
     CHDContext *priv = avctx->priv_data;
@@ -561,50 +560,50 @@ static inline CopyRet copy_frame(AVCodecContext *avctx,
     }
 
     /*
-     * If we're expecting a second field, or we know that the next
-     * picture has the same number as the current picture, then we're
-     * definitely interlaced.
+     * For most content, we can trust the interlaced flag returned
+     * by the hardware, but sometimes we can't. These are the
+     * conditions under which we can trust the flag:
      *
-     * Note that this test can return false negatives if the hardware
-     * hasn't decoded the next picture or if there is a corruption in
-     * the stream. (In either case a 0 will be returned for the next
-     * picture number)
+     * 1) It's not h.264 content
+     * 2) The UNKNOWN_SRC flag is not set
+     * 3) We know we're expecting a second field
+     * 4) The hardware reports this picture and the next picture
+     *    have the same picture number.
+     *
+     * Note that there can still be interlaced content that will
+     * fail this check, if the hardware hasn't decoded the next
+     * picture or if there is a corruption in the stream. (In either
+     * case a 0 will be returned for the next picture number)
      */
-    confirmed_interlaced = ((decoder_status.picNumFlags & ~0x40000000) ==
-                            output->PicInfo.picture_number) ||
-                            priv->need_second_field;
+    trust_interlaced = avctx->codec->id != CODEC_ID_H264 ||
+                       !(output->PicInfo.flags & VDEC_FLAG_UNKNOWN_SRC) ||
+                       priv->need_second_field ||
+                       (decoder_status.picNumFlags & ~0x40000000) ==
+                       output->PicInfo.picture_number;
 
     /*
-     * If we got a false negative for confirmed_interlaced on the first field,
+     * If we got a false negative for trust_interlaced on the first field,
      * we will realise our mistake here when we see that the picture number is that
      * of the previous picture. We cannot recover the frame and should discard the
      * second field to keep the correct number of output frames.
      */
     if (output->PicInfo.picture_number == priv->last_picture && !priv->need_second_field) {
         av_log(avctx, AV_LOG_WARNING,
-               "Incorrectly guessed progressie frame. Discarding second field\n");
+               "Incorrectly guessed progressive frame. Discarding second field\n");
         /* Returning without providing a picture. */
         return RET_OK;
     }
 
-    /*
-     * Testing has, so far, shown that we can't trust the interlaced flag for
-     * H.264 content when VDEC_FLAG_UNKNOWN_SRC is set.
-     */
-    ignore_interlaced = avctx->codec->id == CODEC_ID_H264 &&
-                        (output->PicInfo.flags & VDEC_FLAG_UNKNOWN_SRC) &&
-                        (pic_type == 0 || pic_type == PICT_FRAME ||
-                         !confirmed_interlaced);
-    interlaced        = (output->PicInfo.flags & VDEC_FLAG_INTERLACED_SRC) &&
-                        (!ignore_interlaced || confirmed_interlaced);
-
-    if (ignore_interlaced && (decoder_status.picNumFlags & ~0x40000000) == 0) {
-        av_log(avctx, AV_LOG_WARNING,
+    interlaced = (output->PicInfo.flags & VDEC_FLAG_INTERLACED_SRC) &&
+                 trust_interlaced;
+
+    if (!trust_interlaced && (decoder_status.picNumFlags & ~0x40000000) == 0) {
+        av_log(avctx, AV_LOG_VERBOSE,
                "Next picture number unknown. Assuming progressive frame.\n");
     }
 
-    av_log(avctx, AV_LOG_VERBOSE, "Interlaced state: %d | ignore_interlaced %d\n",
-           interlaced, ignore_interlaced);
+    av_log(avctx, AV_LOG_VERBOSE, "Interlaced state: %d | trust_interlaced %d\n",
+           interlaced, trust_interlaced);
 
     if (priv->pic.data[0] && !priv->need_second_field)
         avctx->release_buffer(avctx, &priv->pic);
-- 
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