player: add stream selection by ffmpeg index

Apparently using the stream index is the best way to refer to the same
streams across multiple FFmpeg-using programs, even if the stream index
itself is rarely meaningful in any way.

For Matroska, there are some possible problems, depending how FFmpeg
actually adds streams. Normally they seem to match though.

1 files changed, 17 insertions, 9 deletions

diff --git a/player/loadfile.c b/player/loadfile.c
index 470e0d24eb..b7dab134c7 100644
--- a/player/loadfile.c
+++ b/player/loadfile.c
@@ -340,6 +340,7 @@ static struct track *add_stream_track(struct MPContext *mpctx,
         .type = stream->type,
         .user_tid = find_new_tid(mpctx, stream->type),
         .demuxer_id = stream->demuxer_id,
+        .ff_index = stream->ff_index,
         .title = stream->title,
         .default_track = stream->default_track,
         .attached_picture = stream->attached_picture != NULL,
@@ -378,7 +379,8 @@ static int match_lang(char **langs, char *lang)
  * tid is the track ID requested by the user (-2: deselect, -1: default)
  * lang is a string list, NULL is same as empty list
  * Sort tracks based on the following criteria, and pick the first:
- * 0) track matches tid (always wins)
+ * 0a) track matches ff-index (always wins)
+ * 0b) track matches tid (almost always wins)
  * 1) track is external (no_default cancels this)
  * 1b) track was passed explicitly (is not an auto-loaded subtitle)
  * 2) earlier match in lang list
@@ -414,9 +416,12 @@ static bool compare_track(struct track *t1, struct track *t2, char **langs,
     return t1->user_tid <= t2->user_tid;
 }
 static struct track *select_track(struct MPContext *mpctx,
-                                  enum stream_type type, int tid, char **langs)
+                                  enum stream_type type, int tid, int ffid,
+                                  char **langs)
 {
-    if (tid == -2)
+    if (ffid != -1)
+        tid = -1; // prefer selecting ffid
+    if (tid == -2 || ffid == -2)
         return NULL;
     bool select_fallback = type == STREAM_VIDEO || type == STREAM_AUDIO;
     struct track *pick = NULL;
@@ -426,6 +431,8 @@ static struct track *select_track(struct MPContext *mpctx,
             continue;
         if (track->user_tid == tid)
             return track;
+        if (track->ff_index == ffid)
+            return track;
         if (!pick || compare_track(track, pick, langs, mpctx->opts))
             pick = track;
     }
@@ -1094,15 +1101,16 @@ goto_reopen_demuxer: ;
     check_previous_track_selection(mpctx);
 
     mpctx->current_track[0][STREAM_VIDEO] =
-        select_track(mpctx, STREAM_VIDEO, mpctx->opts->video_id, NULL);
+        select_track(mpctx, STREAM_VIDEO, opts->video_id, opts->video_id_ff,
+                     NULL);
     mpctx->current_track[0][STREAM_AUDIO] =
-        select_track(mpctx, STREAM_AUDIO, mpctx->opts->audio_id,
-                     mpctx->opts->audio_lang);
+        select_track(mpctx, STREAM_AUDIO, opts->audio_id, opts->audio_id_ff,
+                     opts->audio_lang);
     mpctx->current_track[0][STREAM_SUB] =
-        select_track(mpctx, STREAM_SUB, mpctx->opts->sub_id,
-                     mpctx->opts->sub_lang);
+        select_track(mpctx, STREAM_SUB, opts->sub_id, opts->sub_id_ff,
+                     opts->sub_lang);
     mpctx->current_track[1][STREAM_SUB] =
-        select_track(mpctx, STREAM_SUB, mpctx->opts->sub2_id, NULL);
+        select_track(mpctx, STREAM_SUB, opts->sub2_id, -2, NULL);
     for (int t = 0; t < STREAM_TYPE_COUNT; t++) {
         for (int i = 0; i < NUM_PTRACKS; i++) {
             struct track *track = mpctx->current_track[i][t];