[YoutubeDL] Make postprocessors declarative

Instead of having to configure PPs in code, this allows us and embedding programs not to worry about imports or finer details, similarly to how we handle IEs.

README.md

@@ -537,6 +537,34 @@ From a Python program, you can embed youtube-dl in a more powerful fashion, like
 
 Most likely, you'll want to use various options. For a list of what can be done, have a look at [youtube_dl/YoutubeDL.py](https://github.com/rg3/youtube-dl/blob/master/youtube_dl/YoutubeDL.py#L69). For a start, if you want to intercept youtube-dl's output, set a `logger` object.
 
+Here's a more complete example of a program that only outputs errors, and downloads/converts the video as mp3:
+
+
+    import youtube_dl
+
+
+    class MyLogger(object):
+        def debug(self, msg):
+            pass
+
+        def warning(self, msg):
+            pass
+
+        def error(self, msg):
+            print(msg)
+
+    ydl_opts = {
+        'format': 'bestaudio/best',
+        'postprocessors': [{
+            'key': 'FFmpegExtractAudio',
+            'preferredcodec': 'mp3',
+            'preferredquality': '64',
+        }],
+        'logger': MyLogger(),
+    }
+    with youtube_dl.YoutubeDL(ydl_opts) as ydl:
+        ydl.download(['http://www.youtube.com/watch?v=BaW_jenozKc'])
+
 # BUGS
 
 Bugs and suggestions should be reported at: <https://github.com/rg3/youtube-dl/issues> . Unless you were prompted so or there is another pertinent reason (e.g. GitHub fails to accept the bug report), please do not send bug reports via personal email. For discussions, join us in the irc channel #youtube-dl on freenode.

youtube_dl/YoutubeDL.py

@@ -27,6 +27,7 @@ from .compat import (
     compat_cookiejar,
     compat_expanduser,
     compat_http_client,
+    compat_kwargs,
     compat_str,
     compat_urllib_error,
     compat_urllib_request,
@@ -67,7 +68,11 @@ from .cache import Cache
 from .extractor import get_info_extractor, gen_extractors
 from .downloader import get_suitable_downloader
 from .downloader.rtmp import rtmpdump_version
-from .postprocessor import FFmpegMergerPP, FFmpegPostProcessor
+from .postprocessor import (
+    FFmpegMergerPP,
+    FFmpegPostProcessor,
+    get_postprocessor,
+)
 from .version import __version__
 
 
@@ -176,6 +181,11 @@ class YoutubeDL(object):
     extract_flat:      Do not resolve URLs, return the immediate result.
                        Pass in 'in_playlist' to only show this behavior for
                        playlist items.
+    postprocessors:    A list of dictionaries, each with an entry
+                       key:  The name of the postprocessor. See
+                             youtube_dl/postprocessor/__init__.py for a list.
+                       as well as any further keyword arguments for the
+                       postprocessor.
 
     The following parameters are not used by YoutubeDL itself, they are used by
     the FileDownloader:
@@ -256,6 +266,13 @@ class YoutubeDL(object):
             self.print_debug_header()
             self.add_default_info_extractors()
 
+        for pp_def_raw in self.params.get('postprocessors', []):
+            pp_class = get_postprocessor(pp_def_raw['key'])
+            pp_def = dict(pp_def_raw)
+            del pp_def['key']
+            pp = pp_class(self, **compat_kwargs(pp_def))
+            self.add_post_processor(pp)
+
     def warn_if_short_id(self, argv):
         # short YouTube ID starting with dash?
         idxs = [

youtube_dl/__init__.py

@@ -40,16 +40,6 @@ from .downloader import (
 )
 from .extractor import gen_extractors
 from .YoutubeDL import YoutubeDL
-from .postprocessor import (
-    AtomicParsleyPP,
-    FFmpegAudioFixPP,
-    FFmpegMetadataPP,
-    FFmpegVideoConvertor,
-    FFmpegExtractAudioPP,
-    FFmpegEmbedSubtitlePP,
-    XAttrMetadataPP,
-    ExecAfterDownloadPP,
-)
 
 
 def _real_main(argv=None):
@@ -212,6 +202,43 @@ def _real_main(argv=None):
     any_printing = opts.geturl or opts.gettitle or opts.getid or opts.getthumbnail or opts.getdescription or opts.getfilename or opts.getformat or opts.getduration or opts.dumpjson or opts.dump_single_json
     download_archive_fn = compat_expanduser(opts.download_archive) if opts.download_archive is not None else opts.download_archive
 
+    # PostProcessors
+    postprocessors = []
+    # Add the metadata pp first, the other pps will copy it
+    if opts.addmetadata:
+        postprocessors.append({'key': 'FFmpegMetadata'})
+    if opts.extractaudio:
+        postprocessors.append({
+            'key': 'FFmpegExtractAudio',
+            'preferredcodec': opts.audioformat,
+            'preferredquality': opts.audioquality,
+            'nopostoverwrites': opts.nopostoverwrites,
+        })
+    if opts.recodevideo:
+        postprocessors.append({
+            'key': 'FFmpegVideoConvertor',
+            'preferedformat': opts.recodevideo,
+        })
+    if opts.embedsubtitles:
+        postprocessors.append({
+            'key': 'FFmpegEmbedSubtitle',
+            'subtitlesformat': opts.subtitlesformat,
+        })
+    if opts.xattrs:
+        postprocessors.append({'key': 'XAttrMetadata'})
+    if opts.embedthumbnail:
+        if not opts.addmetadata:
+            postprocessors.append({'key': 'FFmpegAudioFix'})
+        postprocessors.append({'key': 'AtomicParsley'})
+    # Please keep ExecAfterDownload towards the bottom as it allows the user to modify the final file in any way.
+    # So if the user is able to remove the file before your postprocessor runs it might cause a few problems.
+    if opts.exec_cmd:
+        postprocessors.append({
+            'key': 'ExecAfterDownload',
+            'verboseOutput': opts.verbose,
+            'exec_cmd': opts.exec_cmd,
+        })
+
     ydl_opts = {
         'usenetrc': opts.usenetrc,
         'username': opts.username,
@@ -297,32 +324,10 @@ def _real_main(argv=None):
         'encoding': opts.encoding,
         'exec_cmd': opts.exec_cmd,
         'extract_flat': opts.extract_flat,
+        'postprocessors': postprocessors,
     }
 
     with YoutubeDL(ydl_opts) as ydl:
-        # PostProcessors
-        # Add the metadata pp first, the other pps will copy it
-        if opts.addmetadata:
-            ydl.add_post_processor(FFmpegMetadataPP())
-        if opts.extractaudio:
-            ydl.add_post_processor(FFmpegExtractAudioPP(preferredcodec=opts.audioformat, preferredquality=opts.audioquality, nopostoverwrites=opts.nopostoverwrites))
-        if opts.recodevideo:
-            ydl.add_post_processor(FFmpegVideoConvertor(preferedformat=opts.recodevideo))
-        if opts.embedsubtitles:
-            ydl.add_post_processor(FFmpegEmbedSubtitlePP(subtitlesformat=opts.subtitlesformat))
-        if opts.xattrs:
-            ydl.add_post_processor(XAttrMetadataPP())
-        if opts.embedthumbnail:
-            if not opts.addmetadata:
-                ydl.add_post_processor(FFmpegAudioFixPP())
-            ydl.add_post_processor(AtomicParsleyPP())
-
-        # Please keep ExecAfterDownload towards the bottom as it allows the user to modify the final file in any way.
-        # So if the user is able to remove the file before your postprocessor runs it might cause a few problems.
-        if opts.exec_cmd:
-            ydl.add_post_processor(ExecAfterDownloadPP(
-                verboseOutput=opts.verbose, exec_cmd=opts.exec_cmd))
-
         # Update version
         if opts.update_self:
             update_self(ydl.to_screen, opts.verbose)

youtube_dl/postprocessor/__init__.py

@@ -8,11 +8,16 @@ from .ffmpeg import (
     FFmpegExtractAudioPP,
     FFmpegMergerPP,
     FFmpegMetadataPP,
-    FFmpegVideoConvertor,
+    FFmpegVideoConvertorPP,
 )
 from .xattrpp import XAttrMetadataPP
 from .execafterdownload import ExecAfterDownloadPP
 
+
+def get_postprocessor(key):
+    return globals()[key + 'PP']
+
+
 __all__ = [
     'AtomicParsleyPP',
     'ExecAfterDownloadPP',
@@ -22,6 +27,6 @@ __all__ = [
     'FFmpegMergerPP',
     'FFmpegMetadataPP',
     'FFmpegPostProcessor',
-    'FFmpegVideoConvertor',
+    'FFmpegVideoConvertorPP',
     'XAttrMetadataPP',
 ]

youtube_dl/postprocessor/ffmpeg.py

@@ -236,9 +236,9 @@ class FFmpegExtractAudioPP(FFmpegPostProcessor):
         return self._nopostoverwrites, information
 
 
-class FFmpegVideoConvertor(FFmpegPostProcessor):
+class FFmpegVideoConvertorPP(FFmpegPostProcessor):
     def __init__(self, downloader=None, preferedformat=None):
-        super(FFmpegVideoConvertor, self).__init__(downloader)
+        super(FFmpegVideoConvertorPP, self).__init__(downloader)
         self._preferedformat = preferedformat
 
     def run(self, information):