vd_lavc: by default, output all frames, even corrupted ones

Set the flag CODEC_FLAG_OUTPUT_CORRUPT by default. Note that there is
also CODEC_FLAG2_SHOW_ALL, which is older, but this seems to be ffmpeg
only.

Note that whether you want this enabled depends on the user. Some might
prefer that only good frames are output, while others want the decoder
to try as hard as possible to output _anything_. Since mplayer/mpv is
rather the kind of player that tries hard instead of being "clever", set
the new default to override libavcodec's default.

A nice way to test this is switching video tracks. Since mpv doesn't
wait for the next key frame, it'll start feeding the decoder with a
packet from the middle of the stream.

DOCS/man/en/options.rst

@@ -2631,6 +2631,11 @@ OPTIONS
 
         ``--vd--lavc-o=debug=pict``
 
+``--vd-lavc-show-all=<yes|no>``
+    Show even broken/corrupt frames (default: yes). If this option is set to
+    no, libavcodec won't output frames that were either decoded before an
+    initial keyframe was decoded, or frames that are recognized as corrupted.
+
 ``--vd-lavc-skiploopfilter=<skipvalue> (H.264 only)``
     Skips the loop filter (AKA deblocking) during H.264 decoding. Since
     the filtered frame is supposed to be used as reference for decoding

options/options.c

@@ -755,6 +755,7 @@ const struct MPOpts mp_default_opts = {
         .allow_mimetype = 1,
     },
     .lavc_param = {
+        .show_all = 1,
         .check_hw_profile = 1,
     },
     .input = {

options/options.h

@@ -228,6 +228,7 @@ typedef struct MPOpts {
 
     struct lavc_param {
         int fast;
+        int show_all;
         char *skip_loop_filter_str;
         char *skip_idct_str;
         char *skip_frame_str;

video/decode/vd_lavc.c

@@ -73,6 +73,7 @@ static void uninit(struct dec_video *vd);
 
 const m_option_t lavc_decode_opts_conf[] = {
     OPT_FLAG_CONSTANTS("fast", lavc_param.fast, 0, 0, CODEC_FLAG2_FAST),
+    OPT_FLAG("show-all", lavc_param.show_all, 0),
     OPT_STRING("skiploopfilter", lavc_param.skip_loop_filter_str, 0),
     OPT_STRING("skipidct", lavc_param.skip_idct_str, 0),
     OPT_STRING("skipframe", lavc_param.skip_frame_str, 0),
@@ -421,6 +422,15 @@ static void init_avctx(struct dec_video *vd, const char *decoder,
     avctx->flags |= lavc_param->bitexact;
 
     avctx->flags2 |= lavc_param->fast;
+    if (lavc_param->show_all) {
+#ifdef CODEC_FLAG2_SHOW_ALL
+        avctx->flags2 |= CODEC_FLAG2_SHOW_ALL; // ffmpeg only?
+#endif
+#ifdef CODEC_FLAG_OUTPUT_CORRUPT
+        avctx->flags |= CODEC_FLAG_OUTPUT_CORRUPT; // added with Libav 10
+#endif
+    }
+
     avctx->skip_loop_filter = str2AVDiscard(vd, lavc_param->skip_loop_filter_str);
     avctx->skip_idct = str2AVDiscard(vd, lavc_param->skip_idct_str);
     avctx->skip_frame = str2AVDiscard(vd, lavc_param->skip_frame_str);