[downloader/ffmpeg] Improve simultaneous download and merge

4 files changed, 18 insertions, 12 deletions

diff --git a/README.md b/README.md
index 1a46b25f4..dd9cbc7fc 100644
--- a/README.md
+++ b/README.md
@@ -1179,6 +1179,8 @@ $ yt-dlp -o - BaW_jenozKc
 By default, yt-dlp tries to download the best available quality if you **don't** pass any options.
 This is generally equivalent to using `-f bestvideo*+bestaudio/best`. However, if multiple audiostreams is enabled (`--audio-multistreams`), the default format changes to `-f bestvideo+bestaudio/best`. Similarly, if ffmpeg is unavailable, or if you use yt-dlp to stream to `stdout` (`-o -`), the default becomes `-f best/bestvideo+bestaudio`.
 
+**Deprecation warning**: Latest versions of yt-dlp can stream multiple formats to the stdout simultaneously using ffmpeg. So, in future versions, the default for this will be set to `-f bv*+ba/b` similar to normal downloads. If you want to preserve the `-f b/bv+ba` setting, it is recommended to explicitly specify it in the configuration options.
+
 The general syntax for format selection is `-f FORMAT` (or `--format FORMAT`) where `FORMAT` is a *selector expression*, i.e. an expression that describes format or formats you would like to download.
 
 **tl;dr:** [navigate me to examples](#format-selection-examples).
diff --git a/yt_dlp/YoutubeDL.py b/yt_dlp/YoutubeDL.py
index d9b3ce98d..1afe17639 100644
--- a/yt_dlp/YoutubeDL.py
+++ b/yt_dlp/YoutubeDL.py
@@ -2744,14 +2744,9 @@ class YoutubeDL(object):
                     dl_filename = existing_file(full_filename, temp_filename)
                     info_dict['__real_download'] = False
 
-                    _protocols = set(determine_protocol(f) for f in requested_formats)
-                    if len(_protocols) == 1:  # All requested formats have same protocol
-                        info_dict['protocol'] = _protocols.pop()
-                    directly_mergable = FFmpegFD.can_merge_formats(info_dict, self.params)
                     if dl_filename is not None:
                         self.report_file_already_downloaded(dl_filename)
-                    elif (directly_mergable and get_suitable_downloader(
-                            info_dict, self.params, to_stdout=(temp_filename == '-')) == FFmpegFD):
+                    elif get_suitable_downloader(info_dict, self.params, to_stdout=temp_filename == '-'):
                         info_dict['url'] = '\n'.join(f['url'] for f in requested_formats)
                         success, real_download = self.dl(temp_filename, info_dict)
                         info_dict['__real_download'] = real_download
@@ -2769,7 +2764,7 @@ class YoutubeDL(object):
                                 'The formats won\'t be merged.')
 
                         if temp_filename == '-':
-                            reason = ('using a downloader other than ffmpeg' if directly_mergable
+                            reason = ('using a downloader other than ffmpeg' if FFmpegFD.can_merge_formats(info_dict)
                                       else 'but the formats are incompatible for simultaneous download' if merger.available
                                       else 'but ffmpeg is not installed')
                             self.report_warning(
diff --git a/yt_dlp/downloader/__init__.py b/yt_dlp/downloader/__init__.py
index 739d98c2b..2449c7411 100644
--- a/yt_dlp/downloader/__init__.py
+++ b/yt_dlp/downloader/__init__.py
@@ -10,10 +10,15 @@ from ..utils import (
 def get_suitable_downloader(info_dict, params={}, default=NO_DEFAULT, protocol=None, to_stdout=False):
     info_dict['protocol'] = determine_protocol(info_dict)
     info_copy = info_dict.copy()
-    if protocol:
-        info_copy['protocol'] = protocol
     info_copy['to_stdout'] = to_stdout
-    return _get_suitable_downloader(info_copy, params, default)
+
+    downloaders = [_get_suitable_downloader(info_copy, proto, params, default)
+                   for proto in (protocol or info_copy['protocol']).split('+')]
+    if set(downloaders) == {FFmpegFD} and FFmpegFD.can_merge_formats(info_copy, params):
+        return FFmpegFD
+    elif len(downloaders) == 1:
+        return downloaders[0]
+    return None
 
 
 # Some of these require get_suitable_downloader
@@ -72,7 +77,7 @@ def shorten_protocol_name(proto, simplify=False):
     return short_protocol_names.get(proto, proto)
 
 
-def _get_suitable_downloader(info_dict, params, default):
+def _get_suitable_downloader(info_dict, protocol, params, default):
     """Get the downloader class that can handle the info dict."""
     if default is NO_DEFAULT:
         default = HttpFD
@@ -80,7 +85,7 @@ def _get_suitable_downloader(info_dict, params, default):
     # if (info_dict.get('start_time') or info_dict.get('end_time')) and not info_dict.get('requested_formats') and FFmpegFD.can_download(info_dict):
     #     return FFmpegFD
 
-    protocol = info_dict['protocol']
+    info_dict['protocol'] = protocol
     downloaders = params.get('external_downloader')
     external_downloader = (
         downloaders if isinstance(downloaders, compat_str) or downloaders is None
diff --git a/yt_dlp/downloader/external.py b/yt_dlp/downloader/external.py
index 9c1229cf6..3c0202f22 100644
--- a/yt_dlp/downloader/external.py
+++ b/yt_dlp/downloader/external.py
@@ -327,6 +327,10 @@ class FFmpegFD(ExternalFD):
         # Fixme: This may be wrong when --ffmpeg-location is used
         return FFmpegPostProcessor().available
 
+    @classmethod
+    def supports(cls, info_dict):
+        return all(proto in cls.SUPPORTED_PROTOCOLS for proto in info_dict['protocol'].split('+'))
+
     def on_process_started(self, proc, stdin):
         """ Override this in subclasses  """
         pass