Changes

.gitignore

@@ -3,3 +3,4 @@ nohup.out
 venv
 downloads
 cookies.txt
+.yt-dlp-cache/

app.py

@@ -14,16 +14,40 @@ CACHE_DIR    = os.path.join(os.path.dirname(__file__), ".yt-dlp-cache")
 os.makedirs(DOWNLOAD_DIR, exist_ok=True)
 os.makedirs(CACHE_DIR, exist_ok=True)
 
+# Sanity-check write permissions at startup
+_test = os.path.join(DOWNLOAD_DIR, ".write_test")
+try:
+    open(_test, "w").close()
+    os.remove(_test)
+except OSError as e:
+    raise RuntimeError(f"DOWNLOAD_DIR is not writable: {e}")
+
 jobs = {}
 
 AUDIO_FORMATS = ["mp3", "aac", "m4a", "opus", "flac", "wav", "vorbis", "alac"]
 VIDEO_FORMATS = ["mp4", "mkv", "webm", "mov", "avi", "flv"]
 
+# ---------------------------------------------------------------------------
+# Maps each output container to the audio codec FFmpeg should use when
+# merging. "copy" means the audio stream is passed through without
+# re-encoding (safe when the container supports the source codec).
+# Containers like mp4/mov/avi are strict about which audio codecs they
+# accept, so we re-encode to a known-compatible codec for those.
+# ---------------------------------------------------------------------------
+CONTAINER_AUDIO = {
+    "mp4":  "aac",   # opus/webm audio is incompatible with mp4
+    "mov":  "aac",   # same restriction as mp4
+    "avi":  "mp3",   # avi supports mp3 broadly
+    "flv":  "aac",   # flv works with aac
+    "mkv":  "copy",  # mkv supports virtually every codec
+    "webm": "copy",  # webm+opus/vorbis is fine as-is
+}
+
 # ---------------------------------------------------------------------------
 # In-memory info cache — avoids hitting YouTube again for the same URL
 # within INFO_CACHE_TTL seconds (10 minutes).
 # ---------------------------------------------------------------------------
-_info_cache = {}          # url -> {"data": {...}, "ts": float}
+_info_cache = {}
 _info_lock  = threading.Lock()
 INFO_CACHE_TTL = 600  # seconds
 
@@ -56,23 +80,12 @@ def _random_ua():
 # ---------------------------------------------------------------------------
 # Cookies file — place a cookies.txt (Netscape format, exported from your
 # browser while logged into YouTube) next to app.py to authenticate requests.
-# Authenticated sessions are routed to faster CDN endpoints and bypass the
-# throttling YouTube applies to anonymous traffic.
 # The file is optional; if absent yt-dlp falls back to anonymous mode.
 # ---------------------------------------------------------------------------
 COOKIES_FILE = os.path.join(os.path.dirname(__file__), "cookies.txt")
 
 # ---------------------------------------------------------------------------
 # Base yt-dlp options shared by all calls.
-#
-# cookiefile      - browser cookies for authenticated (fast) CDN routing.
-# cachedir        - persists solved JS sig/nsig to disk so node only re-runs
-#                   when YouTube rotates their player (every few days).
-# http_chunk_size - 10 MB chunks; plays nicer with YouTube CDN.
-# js_runtimes     - use local node v20+ for JS challenge solving.
-#
-# NOTE: sleep_interval intentionally removed — it was artificially capping
-#       download speed. Anti-throttle measures live in the frontend instead.
 # ---------------------------------------------------------------------------
 def _base_opts(extra=None):
     opts = {
@@ -117,33 +130,49 @@ def run_download(job_id, url, fmt, chosen_format):
         common = _base_opts({"progress_hooks": [progress_hook]})
 
         if fmt == "audio":
-            codec = chosen_format or "mp3"
+            # Sanitize codec choice — fall back to mp3 if unrecognised
+            codec = chosen_format if chosen_format in AUDIO_FORMATS else "mp3"
             ydl_opts = {
                 **common,
                 "format": "bestaudio/best",
-                "outtmpl": os.path.join(DOWNLOAD_DIR, f"{job_id}_%(title)s.%(ext)s"),
+                # Use only the job_id in the filename to avoid OS-level
+                # permission errors caused by special characters in titles.
+                "outtmpl": os.path.join(DOWNLOAD_DIR, f"{job_id}.%(ext)s"),
+                "tmpdir": DOWNLOAD_DIR,
                 "postprocessors": [{
                     "key": "FFmpegExtractAudio",
                     "preferredcodec": codec,
                     "preferredquality": "192",
                 }],
             }
+
         else:
-            video_fmt = chosen_format or "mp4"
+            # Sanitize container choice — fall back to mp4 if unrecognised
+            video_fmt   = chosen_format if chosen_format in VIDEO_FORMATS else "mp4"
+            # Look up the audio codec compatible with this container.
+            # mkv/webm streams are copied as-is; mp4/mov/avi/flv re-encode
+            # audio so FFmpeg doesn't refuse the merge.
+            audio_codec = CONTAINER_AUDIO.get(video_fmt, "aac")
+
             ydl_opts = {
                 **common,
+                # Let yt-dlp freely pick the best video+audio streams without
+                # restricting by extension — quality is maximised this way.
                 "format": "bestvideo+bestaudio/best",
-                "outtmpl": os.path.join(DOWNLOAD_DIR, f"{job_id}_%(title)s.%(ext)s"),
+                "outtmpl": os.path.join(DOWNLOAD_DIR, f"{job_id}.%(ext)s"),
+                "tmpdir": DOWNLOAD_DIR,
                 "merge_output_format": video_fmt,
-                "postprocessors": [{
+                # Pass codec flags directly to the FFmpeg merge step:
-                    "key": "FFmpegVideoConvertor",
+                #   -c:v copy  — video is never re-encoded (fast, lossless)
-                    "preferedformat": video_fmt,
+                #   -c:a ...   — audio copied or re-encoded as needed
-                }],
+                "postprocessor_args": {
+                    "merger": ["-c:v", "copy", "-c:a", audio_codec]
+                },
             }
 
         with yt_dlp.YoutubeDL(ydl_opts) as ydl:
             info  = ydl.extract_info(url, download=True)
-            title = info.get("title", "video")
+            title = sanitize_filename(info.get("title", "video"))
 
         files = [f for f in os.listdir(DOWNLOAD_DIR) if f.startswith(job_id)]
         if files:
@@ -238,13 +267,20 @@ def download_file(job_id):
     job = jobs.get(job_id)
     if not job or job.get("status") != "done":
         return jsonify({"error": "File not ready"}), 404
+
     filepath = os.path.join(DOWNLOAD_DIR, job["filename"])
     if not os.path.exists(filepath):
         return jsonify({"error": "File missing"}), 404
+
+    # Serve the file with the original (sanitized) video title as the
+    # download name, preserving the correct extension.
+    ext           = os.path.splitext(job["filename"])[1]
+    download_name = f"{job['title']}{ext}"
+
     return send_file(
         filepath,
         as_attachment=True,
-        download_name=job["filename"].split("_", 1)[-1],
+        download_name=download_name,
     )
 
 

start.sh

@@ -6,5 +6,5 @@ if [ -f $FILE ]; then
 fi
 fuser -k 5000/tcp
 source venv/bin/activate
-nohup python app.py &
+python app.py 
-echo $! > $FILE
+echo $$ > $FILE

static/app.js

@@ -6,6 +6,9 @@ let currentFetchController = null;
 
 let availableFormats = { audio: [], video: [] };
 
+const TEXT_DOWNLOADING  = "Descargando...";
+const TEXT_DOWNLOAD = "Descargar";
+const TEXT_COMPLETED = "Completed";
 // ---------------------------------------------------------------------------
 // Only fire /info when the input looks like a real supported URL.
 // ---------------------------------------------------------------------------
@@ -134,7 +137,7 @@ async function startDownload() {
 
   document.getElementById('download-btn-wrap').style.display = 'none';
   document.getElementById('progress-box').classList.add('visible');
-  document.getElementById('progress-label').textContent = 'Downloading...';
+  document.getElementById('progress-label').textContent = TEXT_DOWNLOADING;
   document.getElementById('progress-fill').style.width  = '0%';
   document.getElementById('prog-pct').textContent       = '0%';
   document.getElementById('prog-speed').textContent     = '';
@@ -169,7 +172,7 @@ function pollStatus(jobId) {
 
       if (data.status === 'done') {
         clearInterval(pollTimer);
-        document.getElementById('progress-label').textContent = 'Complete!';
+        document.getElementById('progress-label').textContent = TEXT_COMPLETED;
         document.getElementById('prog-speed').textContent     = '';
         showStatus('✓ Download ready: ' + (data.title || 'file'), 'success');
         document.getElementById('dl-link').href              = '/file/' + jobId;
@@ -188,7 +191,7 @@ function pollStatus(jobId) {
 
 function resetBtn() {
   const btn = document.getElementById('start-btn');
-  btn.disabled = false; btn.innerHTML = 'Download';
+  btn.disabled = false; btn.innerHTML = TEXT_DOWNLOAD;
 }
 
 // ---------------------------------------------------------------------------

yt-dlp.conf

@@ -0,0 +1,25 @@
+# yt-dlp configuration file
+# Place this at ~/.config/yt-dlp/config
+# yt-dlp reads this automatically on every invocation — including ones
+# spawned by Flask — so no flags need to be passed in code.
+
+# ------------------------------------------------------------------
+# Cache — persists the YouTube player JS and API responses to disk.
+# The player is re-used across all downloads until YouTube rotates it
+# (typically every few days), eliminating the repeated
+# "Downloading player / Solving JS challenges" steps.
+# ------------------------------------------------------------------
+--cache-dir ~/.cache/yt-dlp
+
+# ------------------------------------------------------------------
+# JS runtime — node for solving YouTube's JS challenges.
+# Avoids yt-dlp having to search PATH on every invocation.
+# ------------------------------------------------------------------
+--js-runtimes node:/usr/bin/node
+
+# ------------------------------------------------------------------
+# Network
+# ------------------------------------------------------------------
+--socket-timeout 30
+--retries 6
+--fragment-retries 6