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[FFmpeg-devel,v3,1/4] avformat: Introduce AV_DISPOSITION_URGENT disposition flag for emergency alert

Message ID 20210717023829.84846-1-xqq@xqq.im
State New
Headers show
Series [FFmpeg-devel,v3,1/4] avformat: Introduce AV_DISPOSITION_URGENT disposition flag for emergency alert
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Commit Message

zheng qian July 17, 2021, 2:38 a.m. UTC
This patchset introduces AV_DISPOSITION_URGENT disposition flag for
marking stuffs which is expected to be shown immediately as received,
and adds recognization/remuxing support for ARIB superimpose stream.

ARIB superimpose is almost same as ARIB caption but is utilized to
transmit emergency alert and newsflash in Japan DTV.

Since superimpose is designed to be displayed immediately as received,
ARIB superimpose utilizes mpegts private_stream_2 rather than the
private_stream_1 that is used by arib_caption, which means superimpose
packet doesn't have PTS/DTS (AV_NOPTS_VALUE).

Purpose of introducing AV_DISPOSITION_URGENT is mainly:

1) To be able to mark stuffs as "show as received", which could be NOPTS

2) Let ffmpeg-based player to be able to recognize these stuffs such as
ARIB superimpose stream, and extract data to render it onto screen

3) Let mpegtsenc to be able to remux ARIB superimpose stream correctly

Signed-off-by: zheng qian <xqq@xqq.im>
 libavformat/avformat.h | 1 +
 libavformat/dump.c     | 2 ++
 2 files changed, 3 insertions(+)
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diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 81d2ac38d0..6c7d3fb3a5 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -831,6 +831,7 @@  typedef struct AVStreamInternal AVStreamInternal;
 #define AV_DISPOSITION_METADATA     0x40000
 #define AV_DISPOSITION_DEPENDENT    0x80000 ///< dependent audio stream (mix_type=0 in mpegts)
 #define AV_DISPOSITION_STILL_IMAGE 0x100000 ///< still images in video stream (still_picture_flag=1 in mpegts)
+#define AV_DISPOSITION_URGENT      0x200000 ///< stream which is expected to be shown immediately as received (emergency alert)
  * Options for behavior on timestamp wrap detection.
diff --git a/libavformat/dump.c b/libavformat/dump.c
index cf892de107..a987d097dc 100644
--- a/libavformat/dump.c
+++ b/libavformat/dump.c
@@ -610,6 +610,8 @@  static void dump_stream_format(const AVFormatContext *ic, int i,
         av_log(NULL, AV_LOG_INFO, " (dependent)");
     if (st->disposition & AV_DISPOSITION_STILL_IMAGE)
         av_log(NULL, AV_LOG_INFO, " (still image)");
+    if (st->disposition & AV_DISPOSITION_URGENT)
+        av_log(NULL, AV_LOG_INFO, " (urgent)");
     av_log(NULL, AV_LOG_INFO, "\n");
     dump_metadata(NULL, st->metadata, "    ");