[FFmpeg-devel] [PATCH] avformat/rtp: Pass sources and block filter addresses via sdp file for rtp

[Marton Balint]

On Tue, 7 Apr 2020, phunkyfish wrote:

> ---
> libavformat/rtsp.c | 48 +++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 39 insertions(+), 9 deletions(-)
>
> diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
> index cd6fc32a29..dad3f7915e 100644
> --- a/libavformat/rtsp.c
> +++ b/libavformat/rtsp.c
> @@ -21,6 +21,7 @@
> 
> #include "libavutil/avassert.h"
> #include "libavutil/base64.h"
> +#include "libavutil/bprint.h"
> #include "libavutil/avstring.h"
> #include "libavutil/intreadwrite.h"
> #include "libavutil/mathematics.h"
> @@ -2447,7 +2448,7 @@ static int rtp_probe(const AVProbeData *p)
> static int rtp_read_header(AVFormatContext *s)
> {
>     uint8_t recvbuf[RTP_MAX_PACKET_LENGTH];
> -    char host[500], sdp[500];
> +    char host[500], filters_buf[1000];
>     int ret, port;
>     URLContext* in = NULL;
>     int payload_type;
> @@ -2456,6 +2457,8 @@ static int rtp_read_header(AVFormatContext *s)
>     AVIOContext pb;
>     socklen_t addrlen = sizeof(addr);
>     RTSPState *rt = s->priv_data;
> +    const char *p;
> +    AVBPrint sdp;
>
>     if (!ff_network_init())
>         return AVERROR(EIO);
> @@ -2513,16 +2516,38 @@ static int rtp_read_header(AVFormatContext *s)
>     av_url_split(NULL, 0, NULL, 0, host, sizeof(host), &port,
>                  NULL, 0, s->url);
> 
> -    snprintf(sdp, sizeof(sdp),
> -             "v=0\r\nc=IN IP%d %s\r\nm=%s %d RTP/AVP %d\r\n",
> -             addr.ss_family == AF_INET ? 4 : 6, host,
> -             par->codec_type == AVMEDIA_TYPE_DATA  ? "application" :
> -             par->codec_type == AVMEDIA_TYPE_VIDEO ? "video" : "audio",
> -             port, payload_type);
> -    av_log(s, AV_LOG_VERBOSE, "SDP:\n%s\n", sdp);
> +    av_bprint_init(&sdp, 0, AV_BPRINT_SIZE_UNLIMITED);

You may also use AV_BPRINT_SIZE_AUTOMATIC in which case you will get a 
static buffer which will be limited (roughly 1000 chars) but you don't 
have to free it with av_bprint_finalize().

> +    av_bprintf(&sdp, "v=0\r\nc=IN IP%d %s\r\n",
> +               addr.ss_family == AF_INET ? 4 : 6, host);
> +
> +    p = strchr(s->url, '?');
> +    if (p) {
> +        static const char *filters[][2] = {{"sources", "incl"}, {"block", "excl"}, {NULL, NULL}};
> +        int i;
> +        char *q;
> +        for (i = 0; filters[i][0]; i++) {
> +            if (av_find_info_tag(filters_buf, sizeof(filters_buf), filters[i][0], p)) {
> +                q = filters_buf;
> +                while ((q = strchr(q, ',')) != NULL)
> +                    *q = ' ';
> +                av_bprintf(&sdp, "a=source-filter:%s IN IP%d %s %s\r\n",
> +                           filters[i][1],
> +                           addr.ss_family == AF_INET ? 4 : 6, host,
> +                           filters_buf);
> +            }
> +        }
> +    }
> +
> +    av_bprintf(&sdp, "m=%s %d RTP/AVP %d\r\n",
> +               par->codec_type == AVMEDIA_TYPE_DATA  ? "application" :
> +               par->codec_type == AVMEDIA_TYPE_VIDEO ? "video" : "audio",
> +               port, payload_type);
> +    av_log(s, AV_LOG_VERBOSE, "SDP:\n%s\n", sdp.str);
> +    if (av_bprint_is_complete(&sdp))

I think this check should be negated here, because you want to report 
error if the buffer is truncated, not if it is complete.

> +        goto fail_nobuf;
>     avcodec_parameters_free(&par);
> 
> -    ffio_init_context(&pb, sdp, strlen(sdp), 0, NULL, NULL, NULL, NULL);
> +    ffio_init_context(&pb, sdp.str, strlen(sdp.str), 0, NULL, NULL, NULL, NULL);

You can use sdp.len instead of strlen().

>     s->pb = &pb;
>
>     /* sdp_read_header initializes this again */
> @@ -2532,9 +2557,14 @@ static int rtp_read_header(AVFormatContext *s)
>
>     ret = sdp_read_header(s);
>     s->pb = NULL;
> +    av_bprint_finalize(&sdp, NULL);
>     return ret;
> 
> +fail_nobuf:
> +    ret = AVERROR(ENOMEM);
> +    av_log(s, AV_LOG_ERROR, "rtp_read_header(): not enough buffer space for sdp-headers\n");
> fail:
> +    av_bprint_finalize(&sdp, NULL);
>     avcodec_parameters_free(&par);
>     if (in)
>         ffurl_close(in);

Regards,
Marton