From 8e9fc34242f62860f998b5e59f1eeec74ffdd87f Mon Sep 17 00:00:00 2001
From: Artem Eltyshev <elty@yandex-team.ru>
Date: Mon, 3 Aug 2020 23:52:41 +0300
Subject: [PATCH] add explicit maps option

---
 ffmpeg/_run.py              | 12 ++++++------
 ffmpeg/tests/test_ffmpeg.py | 26 ++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/ffmpeg/_run.py b/ffmpeg/_run.py
index c9cbb7c..49d4416 100644
--- a/ffmpeg/_run.py
+++ b/ffmpeg/_run.py
@@ -110,7 +110,7 @@ def _get_global_args(node):
     return list(node.args)
 
 
-def _get_output_args(node, stream_name_map):
+def _get_output_args(node, stream_name_map, explicit_maps):
     if node.name != output.__name__:
         raise ValueError('Unsupported output node: {}'.format(node))
     args = []
@@ -123,7 +123,7 @@ def _get_output_args(node, stream_name_map):
         stream_name = _format_input_stream_name(
             stream_name_map, edge, is_final_arg=True
         )
-        if stream_name != '0' or len(node.incoming_edges) > 1:
+        if explicit_maps or stream_name != '0' or len(node.incoming_edges) > 1:
             args += ['-map', stream_name]
 
     kwargs = copy.copy(node.kwargs)
@@ -147,7 +147,7 @@ def _get_output_args(node, stream_name_map):
 
 
 @output_operator()
-def get_args(stream_spec, overwrite_output=False):
+def get_args(stream_spec, overwrite_output=False, explicit_maps=False):
     """Build command-line arguments to be passed to ffmpeg."""
     nodes = get_stream_spec_nodes(stream_spec)
     args = []
@@ -163,7 +163,7 @@ def get_args(stream_spec, overwrite_output=False):
     if filter_arg:
         args += ['-filter_complex', filter_arg]
     args += reduce(
-        operator.add, [_get_output_args(node, stream_name_map) for node in output_nodes]
+        operator.add, [_get_output_args(node, stream_name_map, explicit_maps) for node in output_nodes]
     )
     args += reduce(operator.add, [_get_global_args(node) for node in global_nodes], [])
     if overwrite_output:
@@ -172,7 +172,7 @@ def get_args(stream_spec, overwrite_output=False):
 
 
 @output_operator()
-def compile(stream_spec, cmd='ffmpeg', overwrite_output=False):
+def compile(stream_spec, cmd='ffmpeg', overwrite_output=False, explicit_maps=False):
     """Build command-line for invoking ffmpeg.
 
     The :meth:`run` function uses this to build the command line
@@ -187,7 +187,7 @@ def compile(stream_spec, cmd='ffmpeg', overwrite_output=False):
         cmd = [cmd]
     elif type(cmd) != list:
         cmd = list(cmd)
-    return cmd + get_args(stream_spec, overwrite_output=overwrite_output)
+    return cmd + get_args(stream_spec, overwrite_output=overwrite_output, explicit_maps=explicit_maps)
 
 
 @output_operator()
diff --git a/ffmpeg/tests/test_ffmpeg.py b/ffmpeg/tests/test_ffmpeg.py
index 51ee258..e60bcc7 100644
--- a/ffmpeg/tests/test_ffmpeg.py
+++ b/ffmpeg/tests/test_ffmpeg.py
@@ -577,6 +577,32 @@ def test__merge_outputs():
     assert ffmpeg.get_args([out1, out2]) == ['-i', 'in.mp4', 'out2.mp4', 'out1.mp4']
 
 
+def test__explicit_maps():
+    in_ = ffmpeg.input('in.mp4')
+    out1 = in_.output('out1.mp4')
+    out2 = in_.output('out2.mp4')
+    assert ffmpeg.merge_outputs(out1, out2).get_args(explicit_maps=True) == [
+        '-i',
+        'in.mp4',
+        '-map',
+        '0',
+        'out1.mp4',
+        '-map',
+        '0',
+        'out2.mp4',
+    ]
+    assert ffmpeg.get_args([out1, out2], explicit_maps=True) == [
+        '-i',
+        'in.mp4',
+        '-map',
+        '0',
+        'out2.mp4',
+        '-map',
+        '0',
+        'out1.mp4'
+    ]
+
+
 def test__input__start_time():
     assert ffmpeg.input('in', ss=10.5).output('out').get_args() == [
         '-ss',