Re: [FFmpeg-devel] [PATCH] avcodec/avformat: Store SDP attributes from RTSP stream into AVStream side data.

[Bernardo Pilarz via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

Hi,

I've tried to push this patch several times, but it looks like my email client is messing up the diff, and patchwork isn't able to apply it.

On 09/07/2024 12:02, Bernardo Pilarz via ffmpeg-devel wrote:
> Connecting to an RTSP stream will now cause the SDP attributes of each media
> stream to be stored in the codecpar of the relative AVStream.
> The SDP attributes are stored in the coded_side_data using the (new) type
> AV_PKT_DATA_SDP_ATTRIBUTES (AVPacketSideDataType enum).
>
> Signed-off-by: bpilarz <bernardo.pilarz@aitek.it>
> ---
>  libavcodec/packet.h |  7 ++++
>  libavformat/rtsp.c  | 97 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 104 insertions(+)
>
> diff --git a/libavcodec/packet.h b/libavcodec/packet.h
> index 13667ffa36..3091c3ce56
> --- a/libavcodec/packet.h
> +++ b/libavcodec/packet.h
> @@ -339,6 +339,13 @@ enum AVPacketSideDataType {
>       */
>      AV_PKT_DATA_FRAME_CROPPING,
>
> +    /**
> +     * Attributes found in the SDP, associated with the stream. This is a
> +     * list of zero terminated key/value strings. There is no end marker for
> +     * the list, so it is required to rely on the side data size to stop.
> +     */
> +    AV_PKT_DATA_SDP_ATTRIBUTES,
> +
>      /**
>       * The number of side data types.
>       * This is not part of the public API/ABI in the sense that it may
> diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
> index 19b93df839..10594e501a
> --- a/libavformat/rtsp.c
> +++ b/libavformat/rtsp.c
> @@ -283,6 +283,91 @@ static int init_satip_stream(AVFormatContext *s)
>  }
>  #endif
>
> +static int sdp_add_attribute_to_stream_side_data(AVFormatContext *s,
> +                                                 AVStream *st,
> +                                                 const char *p)
> +{
> +    AVPacketSideData *side_data = NULL;
> +    AVDictionary* attributes_dict = NULL;
> +    char *key = NULL, *value = NULL;
> +    int ret = 0;
> +
> +    /* Get the stream's attributes dictionary.
> +     * If the stream has no attributes dictionary, it will be automatically
> +     * created by av_dict_set. */
> +    side_data = av_packet_side_data_get(st->codecpar->coded_side_data,
> + st->codecpar->nb_coded_side_data,
> + AV_PKT_DATA_SDP_ATTRIBUTES);
> +    if (side_data) {
> +        ret = av_packet_unpack_dictionary(side_data->data, side_data->size,
> +                                          &attributes_dict);
> +        if (ret) {
> +            av_log(s, AV_LOG_WARNING,
> +                   "Unable to unpack SDP attributes dictionary.\n");
> +            return -1;
> +        }
> +    }
> +
> +    /* The attribute can either be a value attribute (key:value) or
> +     * property attribute (just the key).
> +     * Look for the ':' separator, and create the 'key' and 'value'
> +     * appropriately. */
> +    const char *separator = strchr(p, ':');
> +    if (separator) {
> +        /* Make a copy of the key and value. */
> +        key = av_strndup(p, separator - p);
> +        value = av_strdup(separator + 1);
> +    } else {
> +        /* Copy the key and create an empty value. */
> +        key = av_strdup(p);
> +        value = av_mallocz(1);
> +    }
> +    if (!key || !value) {
> +        av_dict_free(&attributes_dict);
> +        av_free(value);
> +        av_free(key);
> +        return -1;
> +    }
> +
> +    /* Add the attribute, then pack the dictionary again. */
> +    ret = av_dict_set(&attributes_dict, key, value,
> +                      AV_DICT_DONT_STRDUP_KEY |
> +                      AV_DICT_DONT_STRDUP_VAL |
> +                      AV_DICT_MULTIKEY);
> +    if (ret) {
> +        av_log(s, AV_LOG_WARNING,
> +               "Unable to add SDL attribute to dictionary.\n");
> +        av_dict_free(&attributes_dict);
> +        return -1;
> +    }
> +    size_t packed_dict_size = 0u;
> +    uint8_t *packed_dict = av_packet_pack_dictionary(attributes_dict,
> + &packed_dict_size);
> +
> +    /* Free the dictionary, which is not needed any longer. */
> +    av_dict_free(&attributes_dict);
> +
> +    /* Make sure the dictionary was packet successfully, then add it
> +     * back to the stream's side data. */
> +    if (!packed_dict) {
> +        av_log(s, AV_LOG_WARNING,
> +               "Unable to pack SDP attributes dictionary.\n");
> +        return -1;
> +    }
> +    side_data = av_packet_side_data_add(&st->codecpar->coded_side_data,
> + &st->codecpar->nb_coded_side_data,
> + AV_PKT_DATA_SDP_ATTRIBUTES,
> +                                        packed_dict, packed_dict_size,
> +                                        0);
> +    if (!side_data) {
> +        av_log(s, AV_LOG_WARNING,
> +               "Unable to add SDP attributes side data to stream.\n");
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
>  /* parse the rtpmap description: <codec_name>/<clock_rate>[/<other params>] */
>  static int sdp_parse_rtpmap(AVFormatContext *s,
>                              AVStream *st, RTSPStream *rtsp_st,
> @@ -570,6 +655,18 @@ static void sdp_parse_line(AVFormatContext *s, SDPParseState *s1,
>                     sizeof(rtsp_st->control_url));
>          break;
>      case 'a':
> +        /* add all SDP attributes to the stream's side data */
> +        if (rt->nb_rtsp_streams > 0) {
> +            rtsp_st = rt->rtsp_streams[rt->nb_rtsp_streams - 1];
> +            if (rtsp_st->stream_index >= 0) {
> +                st = s->streams[rtsp_st->stream_index];
> +                if (sdp_add_attribute_to_stream_side_data(s, st, p)) {
> +                    av_log(s, AV_LOG_WARNING,
> +                           "Failed to add SDP attribute to stream");
> +                }
> +            }
> +        }
> +        /* now parse the SDP attribute line */
>          if (av_strstart(p, "control:", &p)) {
>              if (rt->nb_rtsp_streams == 0) {
>                  if (!strncmp(p, "rtsp://", 7))

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