avformat_open_input()无法打开URL，初始化网络后仍报错求助

Hey there! Let's break down why avformat_open_input() is still returning a negative error code even after you fixed the network initialization warning with avformat_network_init(). Here are the key steps to diagnose and fix the issue:

1. First, Get the Exact Error Message #

Negative return values from FFmpeg APIs are specific error codes—don’t just ignore them! Use av_strerror() to translate the code into a human-readable message, which will tell you precisely what’s going wrong:

AVFormatContext *fmt_ctx = NULL;
const char *url = "https://mnmedias.api.telequebec.tv/m3u8/29880.m3u8";

int ret = avformat_open_input(&fmt_ctx, url, NULL, NULL);
if (ret < 0) {
    char err_buf[AV_ERROR_MAX_STRING_SIZE];
    av_strerror(ret, err_buf, sizeof(err_buf));
    fprintf(stderr, "avformat_open_input failed: %s (error code: %d)\n", err_buf, ret);
    // Cleanup resources if needed
    return ret;
}

Common errors here might be Protocol not found (missing HTTPS support) or HTTP error 403 Forbidden (access blocked by the server).

2. Verify HTTPS Support in Your FFmpeg Build #

FFmpeg needs a TLS library (like OpenSSL or GnuTLS) compiled in to handle HTTPS URLs. To check:

• Run ffmpeg -protocols in your terminal. Look for https in the list of supported protocols.
• If it’s missing, recompile FFmpeg with TLS support. For example, with OpenSSL:

  ./configure --enable-openssl [your existing build flags]
  make && make install
  

3. Ensure HLS Demuxer is Enabled #

Your target URL is an M3U8 (HLS) stream, so FFmpeg needs the HLS demuxer to parse it. Verify it’s available:

• Run ffmpeg -formats and look for hls under the demuxers (marked with a D flag).
• If missing, recompile FFmpeg with --enable-demuxer=hls (this is usually enabled by default, but custom builds might omit it).

4. Bypass Access Restrictions with Custom Request Headers #

Some servers block requests that don’t mimic a web browser. Try adding a valid User-Agent header to your request:

AVDictionary *opts = NULL;
// Mimic a common desktop browser User-Agent
av_dict_set(&opts, "user_agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36", 0);

int ret = avformat_open_input(&fmt_ctx, url, NULL, &opts);
if (ret < 0) {
    // Handle error
}
av_dict_free(&opts); // Don't forget to free the dictionary!

5. Validate the URL Manually #

First, confirm the URL is reachable and returns valid content:

• Use curl or a web browser to access https://mnmedias.api.telequebec.tv/m3u8/29880.m3u8.
• If you get a 403/404 error, the stream might be expired, geo-restricted, or the server has anti-scraping measures in place.

6. Update Your FFmpeg Version #

Older FFmpeg versions might have bugs with HTTPS handshakes or HLS parsing. Try upgrading to the latest stable release (e.g., 6.x or newer) to rule out version-specific issues.

Start with step 1—getting the exact error message will narrow down the problem immediately!

内容的提问来源于stack exchange，提问作者subha