Downloadable engines (#34)

* Add blender_downloader.py

* Add engine_manager.py

* Add additional methods to engine_manager.py

* Refactor file layout to make engines on par with workers

* Add system platform info to status response

* Default to using system platform / cpu if none are provided

* Add API to download an engine and some general cleanup

* Add method to delete downloaded engine

* Add API calls to download engines and delete downloads

* Misc fixes

src/engines/ffmpeg_engine.py

@@ -0,0 +1,50 @@
+try:
+    from .base_engine import *
+except ImportError:
+    from base_engine import *
+import re
+
+
+class FFMPEG(BaseRenderEngine):
+
+    def version(self):
+        version = None
+        try:
+            ver_out = subprocess.check_output([self.renderer_path(), '-version'],
+                                              timeout=SUBPROCESS_TIMEOUT).decode('utf-8')
+            match = re.match(".*version\s*(\S+)\s*Copyright", ver_out)
+            if match:
+                version = match.groups()[0]
+        except Exception as e:
+            logger.error("Failed to get FFMPEG version: {}".format(e))
+        return version
+
+    def get_encoders(self):
+        raw_stdout = subprocess.check_output([self.renderer_path(), '-encoders'], stderr=subprocess.DEVNULL,
+                                             timeout=SUBPROCESS_TIMEOUT).decode('utf-8')
+        pattern = '(?P<type>[VASFXBD.]{6})\s+(?P<name>\S{2,})\s+(?P<description>.*)'
+        encoders = [m.groupdict() for m in re.finditer(pattern, raw_stdout)]
+        return encoders
+
+    def get_all_formats(self):
+        raw_stdout = subprocess.check_output([self.renderer_path(), '-formats'], stderr=subprocess.DEVNULL,
+                                             timeout=SUBPROCESS_TIMEOUT).decode('utf-8')
+        pattern = '(?P<type>[DE]{1,2})\s+(?P<name>\S{2,})\s+(?P<description>.*)'
+        formats = [m.groupdict() for m in re.finditer(pattern, raw_stdout)]
+        return formats
+
+    def get_output_formats(self):
+        return [x for x in self.get_all_formats() if 'E' in x['type'].upper()]
+
+    def get_frame_count(self, path_to_file):
+        raw_stdout = subprocess.check_output([self.default_renderer_path(), '-i', path_to_file, '-map', '0:v:0', '-c', 'copy',
+                                               '-f', 'null', '-'], stderr=subprocess.STDOUT,
+                                              timeout=SUBPROCESS_TIMEOUT).decode('utf-8')
+        match = re.findall(r'frame=\s*(\d+)', raw_stdout)
+        if match:
+            frame_number = int(match[-1])
+            return frame_number
+
+
+if __name__ == "__main__":
+    print(FFMPEG.get_frame_count('/Users/brett/Desktop/Big_Fire_02.mov'))