Re: [FFmpeg-devel] [PATCH v4] Add new method for playing network based streams with a play rate.

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Rashad Tatum:
> Add implementation for changing the play rate for rtsp streams.
> ---
>  libavformat/avformat.h    |  6 ++++++
>  libavformat/demux.h       |  6 ++++++
>  libavformat/demux_utils.c |  6 ++++++
>  libavformat/rtsp.c        |  1 +
>  libavformat/rtsp.h        | 10 ++++++++++
>  libavformat/rtspdec.c     | 21 +++++++++++++++++++--
>  6 files changed, 48 insertions(+), 2 deletions(-)
> 
> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> index 2034d2aecc..7819b61d3e 100644
> --- a/libavformat/avformat.h
> +++ b/libavformat/avformat.h
> @@ -2358,6 +2358,12 @@ int avformat_flush(AVFormatContext *s);
>   */
>  int av_read_play(AVFormatContext *s);
>  
> +/**
> + * Play a network-based stream (e.g. RTSP stream) with a given play rate
> + * (e.g. Scale value for RTSP) and timestamp position.
> + */
> +int av_read_play_with_rate(AVFormatContext *s, double play_rate, int stream_index, int64_t timestamp);
> +
>  /**
>   * Pause a network-based stream (e.g. RTSP stream).
>   *
> diff --git a/libavformat/demux.h b/libavformat/demux.h
> index e83d84a201..965743bdf0 100644
> --- a/libavformat/demux.h
> +++ b/libavformat/demux.h
> @@ -113,6 +113,12 @@ typedef struct FFInputFormat {
>       * (RTSP).
>       */
>      int (*read_play)(struct AVFormatContext *);
> +    
> +    /**
> +     * Play a network-based stream (e.g. RTSP stream) with a given play rate
> +     * (e.g. Scale value for RTSP) and timestamp position.
> +     */
> +    int (*read_play_with_rate)(struct AVFormatContext *s, double play_rate, int stream_index, int64_t timestamp);
>  
>      /**
>       * Pause playing - only meaningful if using a network-based format
> diff --git a/libavformat/demux_utils.c b/libavformat/demux_utils.c
> index b632277460..8fed41e3b6 100644
> --- a/libavformat/demux_utils.c
> +++ b/libavformat/demux_utils.c
> @@ -179,6 +179,12 @@ int av_read_play(AVFormatContext *s)
>      return AVERROR(ENOSYS);
>  }
>  
> +int av_read_play_with_rate(AVFormatContext *s, double play_rate, int stream_index, int64_t timestamp) {
> +    if (ffifmt(s->iformat)->read_play_with_rate)
> +        return ffifmt(s->iformat)->read_play_with_rate(s, play_rate, stream_index, timestamp);
> +    return AVERROR(ENOSYS); 
> +}
> +
>  int av_read_pause(AVFormatContext *s)
>  {
>      if (ffifmt(s->iformat)->read_pause)
> diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
> index 5ea471b40c..6cfbcdf989 100644
> --- a/libavformat/rtsp.c
> +++ b/libavformat/rtsp.c
> @@ -1998,6 +1998,7 @@ redirect:
>      av_strlcpy(rt->real_challenge, real_challenge, sizeof(rt->real_challenge));
>      rt->state = RTSP_STATE_IDLE;
>      rt->seek_timestamp = 0; /* default is to start stream at position zero */
> +    rt->scale = 1.0; /* default is to play at the normal rate */
>      return 0;
>   fail:
>      ff_rtsp_close_streams(s);
> diff --git a/libavformat/rtsp.h b/libavformat/rtsp.h
> index 83b2e3f4fb..1b8ce05d74 100644
> --- a/libavformat/rtsp.h
> +++ b/libavformat/rtsp.h
> @@ -245,6 +245,16 @@ typedef struct RTSPState {
>       * whenever we resume playback. Either way, the value is only used once,
>       * see rtsp_read_play() and rtsp_read_seek(). */
>      int64_t seek_timestamp;
> +    
> +    /** the scale value requested when calling av_read_play(). This value
> +     * is subsequently used as part of the "Scale" parameter when emitting
> +     * the RTSP PLAY command. The "Scale" parameter determines the stream play 
> +     * rate. A value of 1 represents the normal play rate. Any other value is 
> +     * in regards to the normal play rate. A negative value represents reverse
> +     * playback. If we are currently playing, this command is called instantly. 
> +     * If we are currently paused, this command is called whenever we resume 
> +     * playback.  */
> +    double scale;
>  
>      int seq;                          /**< RTSP command sequence number */
>  
> diff --git a/libavformat/rtspdec.c b/libavformat/rtspdec.c
> index 10078ce2fa..f1e44ccb63 100644
> --- a/libavformat/rtspdec.c
> +++ b/libavformat/rtspdec.c
> @@ -39,6 +39,7 @@
>  #include "tls.h"
>  #include "url.h"
>  #include "version.h"
> +#include <stdio.h>
>  
>  static const struct RTSPStatusMessage {
>      enum RTSPStatusCode code;
> @@ -527,7 +528,7 @@ static int rtsp_read_play(AVFormatContext *s)
>  {
>      RTSPState *rt = s->priv_data;
>      RTSPMessageHeader reply1, *reply = &reply1;
> -    int i;
> +    int i, cmd_char_count = 0;
>      char cmd[MAX_URL_SIZE];
>  
>      av_log(s, AV_LOG_DEBUG, "hello state=%d\n", rt->state);
> @@ -564,11 +565,17 @@ static int rtsp_read_play(AVFormatContext *s)
>          if (rt->state == RTSP_STATE_PAUSED) {
>              cmd[0] = 0;
>          } else {
> -            snprintf(cmd, sizeof(cmd),
> +           
> +            cmd_char_count += snprintf(cmd, sizeof(cmd),
>                       "Range: npt=%"PRId64".%03"PRId64"-\r\n",
>                       rt->seek_timestamp / AV_TIME_BASE,
>                       rt->seek_timestamp / (AV_TIME_BASE / 1000) % 1000);
> +            
> +            snprintf(cmd + cmd_char_count, sizeof(cmd) - cmd_char_count, "Scale: %f\r\n", rt->scale);
> +                     
>          }
> +        
> +       
>          ff_rtsp_send_cmd(s, "PLAY", rt->control_uri, cmd, reply, NULL);
>          if (reply->status_code != RTSP_STATUS_OK) {
>              return ff_rtsp_averror(reply->status_code, -1);
> @@ -593,6 +600,15 @@ static int rtsp_read_play(AVFormatContext *s)
>      return 0;
>  }
>  
> +static int rtsp_read_play_with_rate(AVFormatContext *s, double play_rate, int stream_index, int64_t timestamp) {
> +    RTSPState *rt = s->priv_data;
> +    rt->seek_timestamp = av_rescale_q(timestamp,
> +                                      s->streams[stream_index]->time_base,
> +                                      AV_TIME_BASE_Q);
> +    rt->scale = play_rate;
> +    return rtsp_read_play(s);
> +}
> +
>  /* pause the stream */
>  static int rtsp_read_pause(AVFormatContext *s)
>  {
> @@ -1006,5 +1022,6 @@ const FFInputFormat ff_rtsp_demuxer = {
>      .read_close     = rtsp_read_close,
>      .read_seek      = rtsp_read_seek,
>      .read_play      = rtsp_read_play,
> +    .read_play_with_rate = rtsp_read_play_with_rate,
>      .read_pause     = rtsp_read_pause,
>  };

Seems like play_rate should just be an option of this demuxer (with the
AV_OPT_FLAG_RUNTIME_PARAM flag).

- Andreas

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