如何从ffmpeg中的流中检索HTTP标头？

Question

I'm currently makeing an audio streaming app on Android. I'm using Android NDK combined with ffmpeg to perform that it's working pretty well so far.

Right now I would like to retrieve the shoutcast metadata contained in the headers stream while streaming. Apparently ffmpeg doesn't provide a direct way to do that but I'm pretty sure it's technically possible to retrieve HTTP headers from the stream as we are receiving all the bytes while streaming.

Does anyone know how to retrieve HTTP headers from a stream using ffmpeg?

Answer 1

In case you are looking for shoutcast metadata ...
Since FFmpeg 2.0 there is built-in support for them. Here's the http protocol that exposes the relevant AVOptions.

Implementation

Set the icy AVOption to 1 when calling avformat_open_input . This will set the Icy-MetaData HTTP header when opening the stream:

AVDictionary *options = NULL;
av_dict_set(&options, "icy", "1", 0);
AVFormatContext* container = avformat_alloc_context();
int err = avformat_open_input(&container, url, NULL, &options);

Then poll the icy_metadata_packet or icy_metadata_headers AVOption on your context to retrieve the current metadata:

char* metadata = NULL;
av_opt_get(container, "icy_metadata_packet", AV_OPT_SEARCH_CHILDREN, (uint8_t**) &metadata);
printf("icy_metadata_packet: %s\n", metadata);
av_free(metadata);
metadata = NULL;
av_opt_get(container, "icy_metadata_headers", AV_OPT_SEARCH_CHILDREN, (uint8_t**) &metadata);
printf("\nicy_metadata_headers:\n%s\n", metadata);
av_free(metadata);

Next you'll probably want to get the metadata information up to the Java layer of your Android app. I'm not familiar with the NDK, so you'll have to figure this out for yourself ;)

Example Output

icy_metadata_packet: StreamTitle='Zelda Reorchestrated - Twilight Symphony - Gerudo Desert';

icy_metadata_headers:
icy-br: 192
icy-description: Radio Hyrule
icy-genre: Remix
icy-name: Radio Hyrule
icy-pub: 1
icy-url: http://radiohyrule.com/

More Information

Find out more on the mailing list where the patch was proposed.
The options are defined on the AVClass for the HTTP and HTTPS context ( code ).

Answer 2

This involves 2 separate operations on the http response and has not much to do with android-ffmpeg.

see sections '1.1.3' , '1.1.6' here

Assuming you are using default implementation of HttpClient in android, the apis are very similar. There is a bridge package in use for android that wraps the apache httpclient libs used in my example.

When you get the response, you do one thing to get the response headers ( see links ) and then another thing to get the stream object in the ENTITY and then use JNI to pass a ptr to that stream over to the I/O from ffmpeg.