Revert "libavcodec/mpeg4videodec.c"

This reverts commit 9632275126d4e6a698569c9d4316a300fe98d18f.

I agree with stuartm’s decade old comment on MythTV ticket 3001: H.263 is not a commonly used codec and if these are still bugs, they should be (re-)opened upstream with FFmpeg.

For frame rate “fix” see: October 2005
Closes #509, by applying patch. f851316

however, it has been wrong since October 2014:
Merge commit '7ea1b3472a61de4aa4d41b571e99418e4997ad41'
FFmpeg/FFmpeg@17085a0

lavc: deprecate the use of AVCodecContext.time_base for decoding
FFmpeg/FFmpeg@7ea1b34

-----
for not compiled section see:
Revert [25805], the fix for our workaround created playback problems eaa8f0d

nuv: fix mpeg4 decoding issue in #3001 properly 8082c91

MPEG-4 decode errors as of [12645] https://code.mythtv.org/trac/ticket/3001

Trunk unable to playback MPEG4 files created by mythtranscode https://code.mythtv.org/trac/ticket/8927

mythtv/external/FFmpeg/libavcodec/mpeg4videodec.c

@@ -132,8 +132,6 @@ static inline int mpeg4_is_resync(Mpeg4DecContext *ctx)
     if (s->workaround_bugs & FF_BUG_NO_PADDING && !ctx->resync_marker)
         return 0;
 
-// disabling the while loop since it causes playback issues. see #3001
-#if 0
     while (v <= 0xFF) {
         if (s->pict_type == AV_PICTURE_TYPE_B ||
             (v >> (8 - s->pict_type) != 1) || s->partitioned_frame)
@@ -142,7 +140,6 @@ static inline int mpeg4_is_resync(Mpeg4DecContext *ctx)
         bits_count += 8 + s->pict_type;
         v = show_bits(&s->gb, 16);
     }
-#endif
 
     if (bits_count + 8 >= s->gb.size_in_bits) {
         v >>= 8;
@@ -2395,9 +2392,7 @@ static int decode_vol_header(Mpeg4DecContext *ctx, GetBitContext *gb)
     if (get_bits1(gb) != 0)     /* fixed_vop_rate  */
         s->avctx->framerate.den = get_bits(gb, ctx->time_increment_bits);
     else
-        /* fix for h263 frame rate */
-        s->avctx->time_base.num = (s->avctx->time_base.den>10000) ? 1001 : 1;
-        //s->avctx->framerate.den = 1;
+        s->avctx->framerate.den = 1;
 
     s->avctx->time_base = av_inv_q(av_mul_q(s->avctx->framerate, (AVRational){s->avctx->ticks_per_frame, 1}));