From e54ebaec5229f9f82bc6b77cef5c5b75b7577487 Mon Sep 17 00:00:00 2001
From: wm4 <wm4@nowhere>
Date: Sat, 15 Feb 2020 18:12:12 +0100
Subject: f_decoder_wrapper, sd_add: accept "null" codec

This is for easier use with the "delay_open" feature added in the
previous commit. The "null" codec is reported if the codec is unknown
(because the stream was not opened yet at time the tracks were added).
The rest of the timeline mechanism will set the correct codec at
runtime. But this means every time a delay-loaded track is selected, it
wants to initialize a decoder for the "null" codec.

Accept a "null" decoder. But since FFmpeg has no such codec, and out of
my own laziness, just let it fall back to "common" codecs that need no
other initialization data.
---
 filters/f_decoder_wrapper.c | 8 +++++++-
 sub/sd_ass.c                | 6 +++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/filters/f_decoder_wrapper.c b/filters/f_decoder_wrapper.c
index 7ce13606b6..6f90df04ad 100644
--- a/filters/f_decoder_wrapper.c
+++ b/filters/f_decoder_wrapper.c
@@ -199,13 +199,16 @@ bool mp_decoder_wrapper_reinit(struct mp_decoder_wrapper *d)
     const struct mp_decoder_fns *driver = NULL;
     struct mp_decoder_list *list = NULL;
     char *user_list = NULL;
+    char *fallback = NULL;
 
     if (p->codec->type == STREAM_VIDEO) {
         driver = &vd_lavc;
         user_list = opts->video_decoders;
+        fallback = "h264";
     } else if (p->codec->type == STREAM_AUDIO) {
         driver = &ad_lavc;
         user_list = opts->audio_decoders;
+        fallback = "aac";
 
         if (p->public.try_spdif && p->codec->codec) {
             struct mp_decoder_list *spdif =
@@ -223,7 +226,10 @@ bool mp_decoder_wrapper_reinit(struct mp_decoder_wrapper *d)
         struct mp_decoder_list *full = talloc_zero(NULL, struct mp_decoder_list);
         if (driver)
             driver->add_decoders(full);
-        list = mp_select_decoders(p->log, full, p->codec->codec, user_list);
+        const char *codec = p->codec->codec;
+        if (codec && strcmp(codec, "null") == 0)
+            codec = fallback;
+        list = mp_select_decoders(p->log, full, codec, user_list);
         talloc_free(full);
     }
 
diff --git a/sub/sd_ass.c b/sub/sd_ass.c
index eb80230f44..5443a688d4 100644
--- a/sub/sd_ass.c
+++ b/sub/sd_ass.c
@@ -155,7 +155,11 @@ static int init(struct sd *sd)
     char *extradata = sd->codec->extradata;
     int extradata_size = sd->codec->extradata_size;
 
-    if (strcmp(sd->codec->codec, "ass") != 0) {
+    // Note: accept "null" as alias for "ass", so EDL delay_open subtitle
+    //       streams work.
+    if (strcmp(sd->codec->codec, "ass") != 0 &&
+        strcmp(sd->codec->codec, "null") != 0)
+    {
         ctx->is_converted = true;
         ctx->converter = lavc_conv_create(sd->log, sd->codec->codec, extradata,
                                           extradata_size);
-- 
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