[downloader/fragment] Improve --live-from-start for YouTube livestreams (#2870)

yt_dlp/downloader/fragment.py

@@ -25,6 +25,7 @@ from ..utils import (
     error_to_compat_str,
     encodeFilename,
     sanitized_Request,
+    traverse_obj,
 )
 
 
@@ -382,6 +383,7 @@ class FragmentFD(FileDownloader):
         max_workers = self.params.get('concurrent_fragment_downloads', 1)
         if max_progress > 1:
             self._prepare_multiline_status(max_progress)
+        is_live = any(traverse_obj(args, (..., 2, 'is_live'), default=[]))
 
         def thread_func(idx, ctx, fragments, info_dict, tpe):
             ctx['max_progress'] = max_progress
@@ -395,25 +397,44 @@ class FragmentFD(FileDownloader):
             def __exit__(self, exc_type, exc_val, exc_tb):
                 pass
 
-        spins = []
         if compat_os_name == 'nt':
-            self.report_warning('Ctrl+C does not work on Windows when used with parallel threads. '
-                                'This is a known issue and patches are welcome')
+            def bindoj_result(future):
+                while True:
+                    try:
+                        return future.result(0.1)
+                    except KeyboardInterrupt:
+                        raise
+                    except concurrent.futures.TimeoutError:
+                        continue
+        else:
+            def bindoj_result(future):
+                return future.result()
+
+        spins = []
         for idx, (ctx, fragments, info_dict) in enumerate(args):
             tpe = FTPE(math.ceil(max_workers / max_progress))
-            job = tpe.submit(thread_func, idx, ctx, fragments, info_dict, tpe)
+
+            def interrupt_trigger_iter():
+                for f in fragments:
+                    if not interrupt_trigger[0]:
+                        break
+                    yield f
+
+            job = tpe.submit(thread_func, idx, ctx, interrupt_trigger_iter(), info_dict, tpe)
             spins.append((tpe, job))
 
         result = True
         for tpe, job in spins:
             try:
-                result = result and job.result()
+                result = result and bindoj_result(job)
             except KeyboardInterrupt:
                 interrupt_trigger[0] = False
             finally:
                 tpe.shutdown(wait=True)
-        if not interrupt_trigger[0]:
+        if not interrupt_trigger[0] and not is_live:
             raise KeyboardInterrupt()
+        # we expect the user wants to stop and DO WANT the preceding postprocessors to run;
+        # so returning a intermediate result here instead of KeyboardInterrupt on live
         return result
 
     def download_and_append_fragments(
@@ -431,10 +452,11 @@ class FragmentFD(FileDownloader):
             pack_func = lambda frag_content, _: frag_content
 
         def download_fragment(fragment, ctx):
+            if not interrupt_trigger[0]:
+                return False, fragment['frag_index']
+
             frag_index = ctx['fragment_index'] = fragment['frag_index']
             ctx['last_error'] = None
-            if not interrupt_trigger[0]:
-                return False, frag_index
             headers = info_dict.get('http_headers', {}).copy()
             byte_range = fragment.get('byte_range')
             if byte_range:
@@ -500,8 +522,6 @@ class FragmentFD(FileDownloader):
             self.report_warning('The download speed shown is only of one thread. This is a known issue and patches are welcome')
             with tpe or concurrent.futures.ThreadPoolExecutor(max_workers) as pool:
                 for fragment, frag_content, frag_index, frag_filename in pool.map(_download_fragment, fragments):
-                    if not interrupt_trigger[0]:
-                        break
                     ctx['fragment_filename_sanitized'] = frag_filename
                     ctx['fragment_index'] = frag_index
                     result = append_fragment(decrypt_fragment(fragment, frag_content), frag_index, ctx)