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

[Ross Nicholson]

Great, thanks again. 

A question about AV_BPRINT_SIZE_AUTOMATIC. Is there a heuristic for when to use this versus unlimited?

Or is it that generally if you would have used a buffer of 1000 or less automatic is the right choice?

> On 7 Apr 2020, at 20:50, Marton Balint <cus at passwd.hu> wrote:
> 
> 
> 
>> 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
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