[FFmpeg-soc] shrink rtsp sdp buffer

[Martin Storsjö]

On Wed, 26 May 2010, Josh Allmann wrote:

> The following reverts changes made in r18508 and shrinks the sdp
> buffer in rtsp.c. I only do this because 16k on the stack is a lot.
> 
> This cleans up the last remnants of Vorbis in rtsp.c -- its sdp/fmtp
> processing is now done in rtpdec_xiph.c, so this codepath is not
> touched by Vorbis over RTP anymore except in the case of an error in
> parsing sdp/fmtp. Even then, it should still fall-through rather
> cleanly.

Did you test it?

> Index: libavformat/rtsp.c
> ===================================================================
> --- libavformat/rtsp.c	(revision 23344)
> +++ libavformat/rtsp.c	(working copy)
> @@ -271,9 +271,7 @@
>  static void sdp_parse_fmtp(AVStream *st, const char *p)
>  {
>      char attr[256];
> -    /* Vorbis setup headers can be up to 12KB and are sent base64
> -     * encoded, giving a 12KB * (4/3) = 16KB FMTP line. */
> -    char value[16384];
> +    char value[4096];
>      int i;
>      RTSPStream *rtsp_st = st->priv_data;
>      AVCodecContext *codec = st->codec;

This should be ok.

> @@ -537,10 +535,8 @@
>       * contain long SDP lines containing complete ASF Headers (several
>       * kB) or arrays of MDPR (RM stream descriptor) headers plus
>       * "rulebooks" describing their properties. Therefore, the SDP line
> -     * buffer is large.
> -     *
> -     * The Vorbis FMTP line can be up to 16KB - see sdp_parse_fmtp. */
> -    char buf[16384], *q;
> +     * buffer is large. */
> +    char buf[8192], *q;
>      SDPParseState sdp_parse_state, *s1 = &sdp_parse_state;
>  
>      memset(s1, 0, sizeof(SDPParseState));

You can't shrink this one, since this codepath still is run for all cases, 
even if the RTP depacketizer handles the parsing of fmtp lines itself. 
sdp_parse() calls sdp_parse_line(), which then either calls 
rtsp_st->dynamic_handler->parse_sdp_a_line() or sdp_parse_fmtp(). But the 
comment referring to sdp_parse_fmtp for vorbis should perhaps be updated.

// Martin