[Libav-user] Using FFmpeg programmatically with a proxy

William Seemann wseemann at gmail.com
Fri May 3 06:31:54 CEST 2013

I'm trying to use FFmpeg with a proxy. The following code works if I 
comment out:

     setenv("http_proxy", "", 1);

The proxy server is an instance of Squid]. I know the proxy server is 
working because I can use the same URL with VLC without any issues. With 
the proxy specified, the output from my code is always:

     Proxy path:
     Metadata could not be retrieved -5 // indicates an IO Error
     setDataSource failed, rc is: -1

I compiled FFmpeg with everything enabled. Can someone explain why this 
code doesn't work with a proxy?

     #include <stdio.h>
     #include <stdlib.h>
     #include <libavcodec/avcodec.h>
     #include <libavformat/avformat.h>

     const int SUCCESS = 0;
     const int FAILURE = -1;

     typedef struct State {
         AVFormatContext *pFormatCtx;
         int             audio_stream;
         int             video_stream;
         AVStream        *audio_st;
         AVStream        *video_st;
     } State;

     int setDataSource(State** ps, const char* path) {
         State *state = *ps;

         if (state->pFormatCtx) {

         int ret = 0;

         if ((ret = avformat_open_input(&state->pFormatCtx, path, NULL, 
NULL)) != 0) {
             printf("Metadata could not be retrieved %d\n", ret);
             *ps = NULL;
             return FAILURE;

         if (avformat_find_stream_info(state->pFormatCtx, NULL) < 0) {
             printf("Metadata could not be retrieved\n");
             *ps = NULL;
             return FAILURE;

         *ps = state;
         return SUCCESS;

     const char* extractMetadata(State** ps, const char* key) {
         char* value = NULL;

         State *state = *ps;

         if (!state->pFormatCtx) {
             goto fail;

         if (key) {
             if (av_dict_get(state->pFormatCtx->metadata, key, NULL, 
                 value = av_dict_get(state->pFormatCtx->metadata, key, 


         return value;

     int main(void) {
         setenv("http_proxy", "", 1);

         const char *proxy_path = getenv("http_proxy");

         if (proxy_path) {
             printf("Proxy path: %s\n", proxy_path);
         } else {
             printf("No proxy specified\n");


         State * state = av_mallocz(sizeof(State));

         int ret = setDataSource(&state, "http://<some host>/song.mp3");

         if (ret == 0) {
             printf("setDataSource succedded!\n");
             printf("Artist: %s\n", extractMetadata(&state, "artist"));
         } else {
             printf("setDataSource failed, rc is: %d\n", ret);

         return EXIT_SUCCESS;

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