使用curl作为youtube-dl外部下载器提速无效，求排查与优化方案

Let's tackle your problem step by step—first fixing the curl setup issue, then exploring other speed-boosting options that work without root access.

Why Curl Isn't Speeding Things Up #

Your current code correctly sets external-downloader: 'curl', but curl runs single-threaded by default—just like YouTube-DL's built-in downloader. That's why you don't see any speed improvement. To make curl useful for faster downloads, you need to pass it additional arguments to enable parallel connections and retry logic.

Fixed Code with Optimized Curl Arguments #

Update your ydl_opts to include external-downloader-args with parameters tailored for speed and reliability:

ydl_opts = {
    'format': 'worstaudio/worst',
    'postprocessors': [{
        'key': 'FFmpegExtractAudio',
        'preferredcodec': 'mp3',
        'preferredquality': '192'
    }],
    'outtmpl': 'media/'+result,
    'noplaylist': True,
    'ignoreerrors': True,
    'max-downloads': 1,
    'external-downloader': 'curl',
    # Add curl-specific speed/reliability flags
    'external-downloader-args': '--parallel --parallel-max 4 --retry 5 --retry-delay 2'
}
ydl = youtube_dl.YoutubeDL(ydl_opts)

Here's what those arguments do:

• --parallel: Enables parallel downloading of multiple segments (requires curl 7.66+, which PythonAnywhere should have installed)
• --parallel-max 4: Limits concurrent connections to 4 (stays within PythonAnywhere's network limits)
• --retry 5 & --retry-delay 2: Automatically retries failed downloads 5 times with 2-second gaps, reducing interruptions from unstable connections

Better Alternatives for Speed (No Root Required) #

If curl still doesn't give you the boost you want, these methods work perfectly on PythonAnywhere without admin access:

1. Switch to yt-dlp (Highly Recommended) #

YouTube-DL is no longer actively maintained—yt-dlp is a feature-rich fork that supports multi-threaded downloads out of the box, no external downloader needed. Install it via pip (no root required):

pip install yt-dlp --user

Then adjust your code to use yt-dlp (the API is nearly identical to YouTube-DL):

import yt_dlp

ydl_opts = {
    'format': 'worstaudio/worst',
    'postprocessors': [{
        'key': 'FFmpegExtractAudio',
        'preferredcodec': 'mp3',
        'preferredquality': '192'
    }],
    'outtmpl': 'media/'+result,
    'noplaylist': True,
    'ignoreerrors': True,
    'max-downloads': 1,
    # yt-dlp enables multi-threading by default, but you can tweak it:
    'concurrent_fragment_downloads': 4
}
ydl = yt_dlp.YoutubeDL(ydl_opts)

yt-dlp will automatically split the audio into fragments and download them in parallel, which often doubles or triples download speeds compared to YouTube-DL.

2. Optimize YouTube-DL's Built-In Downloader #

If you must stick with YouTube-DL, tweak its internal downloader settings to improve speed:

• Add 'http_chunk_size': 10485760 to ydl_opts (sets chunk size to 10MB, reducing overhead from frequent small requests)
• Enable 'retries': 5 to handle temporary network blips without aborting downloads

3. Check PythonAnywhere's Network Limits #

Keep in mind that PythonAnywhere's free tier has bandwidth restrictions (100GB/month) and throttling during peak hours. If you're on a free plan, speed increases might be capped by the platform itself—upgrading to a paid tier could resolve this.

4. Adjust Your Audio Format Selection #

While worstaudio/worst minimizes file size, sometimes the corresponding server is slower. Try switching to 'format': 'bestaudio[ext=m4a]/worstaudio'—m4a files are often faster to download and still transcode nicely to 192kbps MP3.

内容的提问来源于stack exchange，提问作者shriniket deshmukh