avformat: deprecate unused MP4A_LATM flag

A generic lavf flag for AAC LATM packetization for the RTP muxer was
added in ef409645f0 and then made inert 20 days later in 0832122880
when a private muxer option was added and the generic flag no longer
read.

doc/formats.texi

@@ -53,8 +53,6 @@ Discard corrupted frames.
 Try to interleave output packets by DTS.
 @item keepside
 Do not merge side data.
-@item latm
-Enable RTP MP4A-LATM payload.
 @item nobuffer
 Reduce the latency introduced by optional buffering
 @item bitexact

libavformat/avformat.h

@@ -1483,7 +1483,9 @@ typedef struct AVFormatContext {
  * This flag is mainly intended for testing.
  */
 #define AVFMT_FLAG_BITEXACT         0x0400
-#define AVFMT_FLAG_MP4A_LATM    0x8000 ///< Enable RTP MP4A-LATM payload
+#if FF_API_LAVF_MP4A_LATM
+#define AVFMT_FLAG_MP4A_LATM    0x8000 ///< Deprecated, does nothing.
+#endif
 #define AVFMT_FLAG_SORT_DTS    0x10000 ///< try to interleave outputted packets by dts (using this flag can slow demuxing down)
 #define AVFMT_FLAG_PRIV_OPT    0x20000 ///< Enable use of private options by delaying codec open (this could be made default once all code is converted)
 #if FF_API_LAVF_KEEPSIDE_FLAG

libavformat/options_table.h

@@ -52,7 +52,9 @@ static const AVOption avformat_options[] = {
 {"keepside", "deprecated, does nothing", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_KEEP_SIDE_DATA }, INT_MIN, INT_MAX, D, "fflags"},
 #endif
 {"fastseek", "fast but inaccurate seeks", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_FAST_SEEK }, INT_MIN, INT_MAX, D, "fflags"},
-{"latm", "enable RTP MP4A-LATM payload", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_MP4A_LATM }, INT_MIN, INT_MAX, E, "fflags"},
+#if FF_API_LAVF_MP4A_LATM
+{"latm", "deprecated, does nothing", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_MP4A_LATM }, INT_MIN, INT_MAX, E, "fflags"},
+#endif
 {"nobuffer", "reduce the latency introduced by optional buffering", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_NOBUFFER }, 0, INT_MAX, D, "fflags"},
 {"bitexact", "do not write random/volatile data", 0, AV_OPT_TYPE_CONST, { .i64 = AVFMT_FLAG_BITEXACT }, 0, 0, E, "fflags" },
 {"shortest", "stop muxing with the shortest stream", 0, AV_OPT_TYPE_CONST, { .i64 = AVFMT_FLAG_SHORTEST }, 0, 0, E, "fflags" },

libavformat/rtpenc_chain.c

@@ -58,7 +58,7 @@ int ff_rtp_chain_mux_open(AVFormatContext **out, AVFormatContext *s,
     rtpctx->max_delay = s->max_delay;
     /* Copy other stream parameters. */
     rtpctx->streams[0]->sample_aspect_ratio = st->sample_aspect_ratio;
-    rtpctx->flags |= s->flags & (AVFMT_FLAG_MP4A_LATM | AVFMT_FLAG_BITEXACT);
+    rtpctx->flags |= s->flags & AVFMT_FLAG_BITEXACT;
 
     /* Get the payload type from the codec */
     if (st->id < RTP_PT_PRIVATE)

libavformat/version.h

@@ -97,6 +97,9 @@
 #ifndef FF_API_DASH_MIN_SEG_DURATION
 #define FF_API_DASH_MIN_SEG_DURATION    (LIBAVFORMAT_VERSION_MAJOR < 59)
 #endif
+#ifndef FF_API_LAVF_MP4A_LATM
+#define FF_API_LAVF_MP4A_LATM           (LIBAVFORMAT_VERSION_MAJOR < 59)
+#endif
 
 
 #ifndef FF_API_R_FRAME_RATE