nut: Support experimental NUT 4 features

Add the low overhead pipe mode and the extended broadcast mode.
Export the options as 'syncponts' since it impacts only that.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

doc/muxers.texi

@@ -444,6 +444,23 @@ Alternatively you can write the command as:
 avconv -benchmark -i INPUT -f null -
 @end example
 
+@section nut
+
+@table @option
+@item -syncpoints @var{flags}
+Change the syncpoint usage in nut:
+@table @option
+@item @var{default} use the normal low-overhead seeking aids.
+@item @var{none} do not use the syncpoints at all, reducing the overhead but making the stream non-seekable;
+@item @var{timestamped} extend the syncpoint with a wallclock field.
+@end table
+The @var{none} and @var{timestamped} flags are experimental.
+@end table
+
+@example
+avconv -i INPUT -f_strict experimental -syncpoints none - | processor
+@end example
+
 @section ogg
 
 Ogg container muxer.

doc/nut.texi

@@ -17,6 +17,27 @@ subtitle and user-defined streams in a simple, yet efficient, way.
 It was created by a group of FFmpeg and MPlayer developers in 2003
 and was finalized in 2008.
 
+@chapter Modes
+NUT has some variants signaled by using the flags field in its main header.
+
+@multitable @columnfractions .4 .4
+@item BROADCAST   @tab Extend the syncpoint to report the sender wallclock
+@item PIPE        @tab Omit completely the syncpoint
+@end multitable
+
+@section BROADCAST
+
+The BROADCAST variant provides a secondary time reference to facilitate
+detecting endpoint latency and network delays.
+It assumes all the endpoint clocks are syncronized.
+To be used in real-time scenarios.
+
+@section PIPE
+
+The PIPE variant assumes NUT is used as non-seekable intermediate container,
+by not using syncpoint removes unneeded overhead and reduces the overall
+memory usage.
+
 @chapter Container-specific codec tags
 
 @section Generic raw YUVA formats

libavformat/nut.h

@@ -36,7 +36,9 @@
 
 #define MAX_DISTANCE (1024*32-1)
 
-#define NUT_VERSION 3
+#define NUT_MAX_VERSION 4
+#define NUT_STABLE_VERSION 3
+#define NUT_MIN_VERSION 2
 
 typedef enum{
     FLAG_KEY        =   1, ///<if set, frame is keyframe
@@ -85,6 +87,7 @@ typedef struct ChapterContext {
 } ChapterContext;
 
 typedef struct NUTContext {
+    const AVClass *av_class;
     AVFormatContext *avf;
 //    int written_packet_size;
 //    int64_t packet_start;
@@ -100,6 +103,10 @@ typedef struct NUTContext {
     int header_count;
     AVRational *time_base;
     struct AVTreeNode *syncpoints;
+#define NUT_BROADCAST 1 // use extended syncpoints
+#define NUT_PIPE 2      // do not write syncpoints
+    int flags;
+    int version; // version currently in use
 } NUTContext;
 
 extern const AVCodecTag ff_nut_subtitle_tags[];

libavformat/nutdec.c

@@ -213,8 +213,8 @@ static int decode_main_header(NUTContext *nut)
     end  = get_packetheader(nut, bc, 1, MAIN_STARTCODE);
     end += avio_tell(bc);
 
-    tmp = ffio_read_varlen(bc);
-    if (tmp < 2 && tmp > NUT_VERSION) {
+    nut->version = ffio_read_varlen(bc);
+    if (tmp < NUT_MIN_VERSION && tmp > NUT_MAX_VERSION) {
         av_log(s, AV_LOG_ERROR, "Version %"PRId64" not supported.\n",
                tmp);
         return AVERROR(ENOSYS);
@@ -320,6 +320,11 @@ static int decode_main_header(NUTContext *nut)
         assert(nut->header_len[0] == 0);
     }
 
+    // flags had been effectively introduced in version 4
+    if (nut->version > NUT_STABLE_VERSION) {
+        nut->flags = ffio_read_varlen(bc);
+    }
+
     if (skip_reserved(bc, end) || ffio_get_checksum(bc)) {
         av_log(s, AV_LOG_ERROR, "main header checksum mismatch\n");
         return AVERROR_INVALIDDATA;
@@ -547,6 +552,14 @@ static int decode_syncpoint(NUTContext *nut, int64_t *ts, int64_t *back_ptr)
     ff_nut_reset_ts(nut, nut->time_base[tmp % nut->time_base_count],
                     tmp / nut->time_base_count);
 
+    if (nut->flags & NUT_BROADCAST) {
+        tmp = ffio_read_varlen(bc);
+        av_log(s, AV_LOG_VERBOSE, "Syncpoint wallclock %"PRId64"\n",
+               av_rescale_q(tmp / nut->time_base_count,
+                            nut->time_base[tmp % nut->time_base_count],
+                            AV_TIME_BASE_Q));
+    }
+
     if (skip_reserved(bc, end) || ffio_get_checksum(bc)) {
         av_log(s, AV_LOG_ERROR, "sync point checksum mismatch\n");
         return AVERROR_INVALIDDATA;
@@ -728,7 +741,8 @@ static int decode_frame_header(NUTContext *nut, int64_t *pts, int *stream_id,
     int size, flags, size_mul, pts_delta, i, reserved_count;
     uint64_t tmp;
 
-    if (avio_tell(bc) > nut->last_syncpoint_pos + nut->max_distance) {
+    if (!(nut->flags & NUT_PIPE) &&
+        avio_tell(bc) > nut->last_syncpoint_pos + nut->max_distance) {
         av_log(s, AV_LOG_ERROR,
                "Last frame must have been damaged %"PRId64" > %"PRId64" + %d\n",
                avio_tell(bc), nut->last_syncpoint_pos, nut->max_distance);
@@ -781,8 +795,9 @@ static int decode_frame_header(NUTContext *nut, int64_t *pts, int *stream_id,
 
     if (flags & FLAG_CHECKSUM) {
         avio_rb32(bc); // FIXME check this
-    } else if (size > 2 * nut->max_distance || FFABS(stc->last_pts - *pts) >
-               stc->max_pts_distance) {
+    } else if (!(nut->flags & NUT_PIPE) &&
+               size > 2 * nut->max_distance ||
+               FFABS(stc->last_pts - *pts) > stc->max_pts_distance) {
         av_log(s, AV_LOG_ERROR, "frame size > 2max_distance and no checksum\n");
         return AVERROR_INVALIDDATA;
     }
@@ -933,6 +948,10 @@ static int read_seek(AVFormatContext *s, int stream_index,
     int64_t pos, pos2, ts;
     int i;
 
+    if (nut->flags & NUT_PIPE) {
+        return AVERROR(ENOSYS);
+    }
+
     if (st->index_entries) {
         int index = av_index_search_timestamp(st, pts, flags);
         if (index < 0)

libavformat/nutenc.c

@@ -25,6 +25,8 @@
 #include "libavutil/mathematics.h"
 #include "libavutil/tree.h"
 #include "libavutil/dict.h"
+#include "libavutil/time.h"
+#include "libavutil/opt.h"
 #include "libavcodec/mpegaudiodata.h"
 #include "nut.h"
 #include "internal.h"
@@ -325,7 +327,7 @@ static void write_mainheader(NUTContext *nut, AVIOContext *bc)
         tmp_head_idx;
     int64_t tmp_match;
 
-    ff_put_v(bc, NUT_VERSION);
+    ff_put_v(bc, nut->version);
     ff_put_v(bc, nut->avf->nb_streams);
     ff_put_v(bc, nut->max_distance);
     ff_put_v(bc, nut->time_base_count);
@@ -405,6 +407,9 @@ static void write_mainheader(NUTContext *nut, AVIOContext *bc)
         ff_put_v(bc, nut->header_len[i]);
         avio_write(bc, nut->header[i], nut->header_len[i]);
     }
+    // flags had been effectively introduced in version 4
+    if (nut->version > NUT_STABLE_VERSION)
+        ff_put_v(bc, nut->flags);
 }
 
 static int write_streamheader(AVFormatContext *avctx, AVIOContext *bc,
@@ -643,6 +648,16 @@ static int nut_write_header(AVFormatContext *s)
 
     nut->avf = s;
 
+    nut->version = NUT_STABLE_VERSION + !!nut->flags;
+    if (nut->flags && s->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL) {
+        av_log(s, AV_LOG_ERROR,
+               "The additional syncpoint modes require version %d, "
+               "that is currently not finalized, "
+               "please set -f_strict experimental in order to enable it.\n",
+               nut->version);
+        return AVERROR_EXPERIMENTAL;
+    }
+
     nut->stream = av_mallocz(sizeof(StreamContext) * s->nb_streams);
     if (s->nb_chapters)
         nut->chapter = av_mallocz(sizeof(ChapterContext) * s->nb_chapters);
@@ -789,7 +804,8 @@ static int nut_write_packet(AVFormatContext *s, AVPacket *pkt)
 
 //FIXME: Ensure store_sp is 1 in the first place.
 
-    if (store_sp) {
+    if (store_sp &&
+        (!(nut->flags & NUT_PIPE) || nut->last_syncpoint_pos == INT_MIN)) {
         Syncpoint *sp, dummy = { .pos = INT64_MAX };
 
         ff_nut_reset_ts(nut, *nus->time_base, pkt->dts);
@@ -815,6 +831,11 @@ static int nut_write_packet(AVFormatContext *s, AVPacket *pkt)
             return ret;
         put_tt(nut, nus->time_base, dyn_bc, pkt->dts);
         ff_put_v(dyn_bc, sp ? (nut->last_syncpoint_pos - sp->pos) >> 4 : 0);
+
+        if (nut->flags & NUT_BROADCAST) {
+            put_tt(nut, nus->time_base, dyn_bc,
+                   av_rescale_q(av_gettime(), AV_TIME_BASE_Q, *nus->time_base));
+        }
         put_packet(nut, bc, dyn_bc, 1, SYNCPOINT_STARTCODE);
 
         if ((ret = ff_nut_add_sp(nut, nut->last_syncpoint_pos, 0 /*unused*/, pkt->dts)) < 0)
@@ -917,7 +938,7 @@ static int nut_write_packet(AVFormatContext *s, AVPacket *pkt)
     nus->last_pts   = pkt->pts;
 
     //FIXME just store one per syncpoint
-    if (flags & FLAG_KEY)
+    if (flags & FLAG_KEY && !(nut->flags & NUT_PIPE))
         av_add_index_entry(
             s->streams[pkt->stream_index],
             nut->last_syncpoint_pos,
@@ -945,6 +966,23 @@ static int nut_write_trailer(AVFormatContext *s)
     return 0;
 }
 
+#define OFFSET(x) offsetof(NUTContext, x)
+#define E AV_OPT_FLAG_ENCODING_PARAM
+static const AVOption options[] = {
+    { "syncpoints",  "NUT syncpoint behaviour",                         OFFSET(flags), AV_OPT_TYPE_FLAGS, {.i64 = 0},             INT_MIN, INT_MAX, E, "syncpoints" },
+    { "default",     "",                                                0,             AV_OPT_TYPE_CONST, {.i64 = 0},             INT_MIN, INT_MAX, E, "syncpoints" },
+    { "none",        "Disable syncpoints, low overhead and unseekable", 0,             AV_OPT_TYPE_CONST, {.i64 = NUT_PIPE},      INT_MIN, INT_MAX, E, "syncpoints" },
+    { "timestamped", "Extend syncpoints with a wallclock timestamp",    0,             AV_OPT_TYPE_CONST, {.i64 = NUT_BROADCAST}, INT_MIN, INT_MAX, E, "syncpoints" },
+    { NULL },
+};
+
+static const AVClass class = {
+    .class_name = "nutenc",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
 AVOutputFormat ff_nut_muxer = {
     .name           = "nut",
     .long_name      = NULL_IF_CONFIG_SMALL("NUT"),
@@ -959,4 +997,5 @@ AVOutputFormat ff_nut_muxer = {
     .write_trailer  = nut_write_trailer,
     .flags          = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS,
     .codec_tag      = ff_nut_codec_tags,
+    .priv_class     = &class,
 };