[fragment] Read downloaded fragments only when needed (#3069)

Authored by: Lesmiscore

yt_dlp/downloader/fragment.py

@@ -133,19 +133,19 @@ class FragmentFD(FileDownloader):
         }
         success = ctx['dl'].download(fragment_filename, fragment_info_dict)
         if not success:
-            return False, None
+            return False
         if fragment_info_dict.get('filetime'):
             ctx['fragment_filetime'] = fragment_info_dict.get('filetime')
         ctx['fragment_filename_sanitized'] = fragment_filename
-        try:
-            return True, self._read_fragment(ctx)
-        except FileNotFoundError:
-            if not info_dict.get('is_live'):
-                raise
-            return False, None
+        return True
 
     def _read_fragment(self, ctx):
-        down, frag_sanitized = self.sanitize_open(ctx['fragment_filename_sanitized'], 'rb')
+        try:
+            down, frag_sanitized = self.sanitize_open(ctx['fragment_filename_sanitized'], 'rb')
+        except FileNotFoundError:
+            if ctx.get('live'):
+                return None
+            raise
         ctx['fragment_filename_sanitized'] = frag_sanitized
         frag_content = down.read()
         down.close()
@@ -457,7 +457,7 @@ class FragmentFD(FileDownloader):
 
         def download_fragment(fragment, ctx):
             if not interrupt_trigger[0]:
-                return False, fragment['frag_index']
+                return
 
             frag_index = ctx['fragment_index'] = fragment['frag_index']
             ctx['last_error'] = None
@@ -467,14 +467,12 @@ class FragmentFD(FileDownloader):
                 headers['Range'] = 'bytes=%d-%d' % (byte_range['start'], byte_range['end'] - 1)
 
             # Never skip the first fragment
-            fatal = is_fatal(fragment.get('index') or (frag_index - 1))
-            count, frag_content = 0, None
+            fatal, count = is_fatal(fragment.get('index') or (frag_index - 1)), 0
             while count <= fragment_retries:
                 try:
-                    success, frag_content = self._download_fragment(ctx, fragment['url'], info_dict, headers)
-                    if not success:
-                        return False, frag_index
-                    break
+                    if self._download_fragment(ctx, fragment['url'], info_dict, headers):
+                        break
+                    return
                 except (compat_urllib_error.HTTPError, http.client.IncompleteRead) as err:
                     # Unavailable (possibly temporary) fragments may be served.
                     # First we try to retry then either skip or abort.
@@ -491,13 +489,9 @@ class FragmentFD(FileDownloader):
                         break
                     raise
 
-            if count > fragment_retries:
-                if not fatal:
-                    return False, frag_index
+            if count > fragment_retries and fatal:
                 ctx['dest_stream'].close()
                 self.report_error('Giving up after %s fragment retries' % fragment_retries)
-                return False, frag_index
-            return frag_content, frag_index
 
         def append_fragment(frag_content, frag_index, ctx):
             if not frag_content:
@@ -520,23 +514,23 @@ class FragmentFD(FileDownloader):
 
             def _download_fragment(fragment):
                 ctx_copy = ctx.copy()
-                frag_content, frag_index = download_fragment(fragment, ctx_copy)
-                return fragment, frag_content, frag_index, ctx_copy.get('fragment_filename_sanitized')
+                download_fragment(fragment, ctx_copy)
+                return fragment, fragment['frag_index'], ctx_copy.get('fragment_filename_sanitized')
 
             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):
+                for fragment, frag_index, frag_filename in pool.map(_download_fragment, fragments):
                     ctx['fragment_filename_sanitized'] = frag_filename
                     ctx['fragment_index'] = frag_index
-                    result = append_fragment(decrypt_fragment(fragment, frag_content), frag_index, ctx)
+                    result = append_fragment(decrypt_fragment(fragment, self._read_fragment(ctx)), frag_index, ctx)
                     if not result:
                         return False
         else:
             for fragment in fragments:
                 if not interrupt_trigger[0]:
                     break
-                frag_content, frag_index = download_fragment(fragment, ctx)
-                result = append_fragment(decrypt_fragment(fragment, frag_content), frag_index, ctx)
+                download_fragment(fragment, ctx)
+                result = append_fragment(decrypt_fragment(fragment, self._read_fragment(ctx)), fragment['frag_index'], ctx)
                 if not result:
                     return False
 

yt_dlp/downloader/ism.py

@@ -263,9 +263,11 @@ class IsmFD(FragmentFD):
             count = 0
             while count <= fragment_retries:
                 try:
-                    success, frag_content = self._download_fragment(ctx, segment['url'], info_dict)
+                    success = self._download_fragment(ctx, segment['url'], info_dict)
                     if not success:
                         return False
+                    frag_content = self._read_fragment(ctx)
+
                     if not extra_state['ism_track_written']:
                         tfhd_data = extract_box_data(frag_content, [b'moof', b'traf', b'tfhd'])
                         info_dict['_download_params']['track_id'] = u32.unpack(tfhd_data[4:8])[0]

yt_dlp/downloader/mhtml.py

@@ -171,9 +171,10 @@ body > figure > img {
                 assert fragment_base_url
                 fragment_url = urljoin(fragment_base_url, fragment['path'])
 
-            success, frag_content = self._download_fragment(ctx, fragment_url, info_dict)
+            success = self._download_fragment(ctx, fragment_url, info_dict)
             if not success:
                 continue
+            frag_content = self._read_fragment(ctx)
 
             mime_type = b'image/jpeg'
             if frag_content.startswith(b'\x89PNG\r\n\x1a\n'):

yt_dlp/downloader/youtube_live_chat.py

@@ -115,9 +115,10 @@ class YoutubeLiveChatFD(FragmentFD):
             count = 0
             while count <= fragment_retries:
                 try:
-                    success, raw_fragment = dl_fragment(url, request_data, headers)
+                    success = dl_fragment(url, request_data, headers)
                     if not success:
                         return False, None, None, None
+                    raw_fragment = self._read_fragment(ctx)
                     try:
                         data = ie.extract_yt_initial_data(video_id, raw_fragment.decode('utf-8', 'replace'))
                     except RegexNotFoundError:
@@ -145,9 +146,10 @@ class YoutubeLiveChatFD(FragmentFD):
 
         self._prepare_and_start_frag_download(ctx, info_dict)
 
-        success, raw_fragment = dl_fragment(info_dict['url'])
+        success = dl_fragment(info_dict['url'])
         if not success:
             return False
+        raw_fragment = self._read_fragment(ctx)
         try:
             data = ie.extract_yt_initial_data(video_id, raw_fragment.decode('utf-8', 'replace'))
         except RegexNotFoundError: