avio: Allow custom IO users to get labels for the output bytestream

This allows callers with avio write callbacks to get the bytestream positions that correspond to keyframes, suitable for live streaming. In the simplest form, a caller could expect that a header is written to the bytestream during the avformat_write_header, and the data output to the avio context during e.g. av_write_frame corresponds exactly to the current packet passed in. When combined with av_interleaved_write_frame, and with muxers that do buffering (most muxers that do some sort of fragmenting or clustering), the mapping from input data to bytestream positions is nontrivial. This allows callers to get directly information about what part of the bytestream is what, without having to resort to assumptions about the muxer behaviour. One keyframe/fragment/block can still be split into multiple (if they are larger than the aviocontext buffer), which would call the callback with e.g. AVIO_DATA_MARKER_SYNC_POINT, followed by AVIO_DATA_MARKER_UNKNOWN for the second time it is called with the following data.

Martin Storsjö committed 10 years ago

Commit db7968b1 parent 8e757715 files · +127 −3Browse files

Unified · Split

5 files

doc/APIchanges +4 −0
libavformat/avio.h +66 −0
libavformat/aviobuf.c +50 −2
libavformat/mux.c +6 −0
libavformat/version.h +1 −1

doc/APIchanges+4−0

@@ -13,6 +13,10 @@ libavutil: 2015-08-28 · 12 unmodified lines
13	13
14	14	API changes, most recent first:
15	15
	16	+2016-xx-xx - xxxxxxx - lavf 57.7.0 - avio.h
	17	+ Add AVIODataMarkerType, write_data_type, ignore_boundary_point and
	18	+ avio_write_marker.
	19	+
16	20	2016-xx-xx - xxxxxxx - lavu 55.12.0 - opt.h
17	21	Add av_stereo3d_type_name() and av_stereo3d_from_name().
18	22

libavformat/avio.h+66−0

@@ -53,6 +53,42 @@ typedef struct AVIOInterruptCB { · 52 unmodified lines
53	53	void *opaque;
54	54	} AVIOInterruptCB;
55	55
	56	+/**
	57	+ * Different data types that can be returned via the AVIO
	58	+ * write_data_type callback.
	59	+ */
	60	+enum AVIODataMarkerType {
	61	+ /**
	62	+ * Header data; this needs to be present for the stream to be decodeable.
	63	+ */
	64	+ AVIO_DATA_MARKER_HEADER,
	65	+ /**
	66	+ * A point in the output bytestream where a decoder can start decoding
	67	+ * (i.e. a keyframe). A demuxer/decoder given the data flagged with
	68	+ * AVIO_DATA_MARKER_HEADER, followed by any AVIO_DATA_MARKER_SYNC_POINT,
	69	+ * should give decodeable results.
	70	+ */
	71	+ AVIO_DATA_MARKER_SYNC_POINT,
	72	+ /**
	73	+ * A point in the output bytestream where a demuxer can start parsing
	74	+ * (for non self synchronizing bytestream formats). That is, any
	75	+ * non-keyframe packet start point.
	76	+ */
	77	+ AVIO_DATA_MARKER_BOUNDARY_POINT,
	78	+ /**
	79	+ * This is any, unlabelled data. It can either be a muxer not marking
	80	+ * any positions at all, it can be an actual boundary/sync point
	81	+ * that the muxer chooses not to mark, or a later part of a packet/fragment
	82	+ * that is cut into multiple write callbacks due to limited IO buffer size.
	83	+ */
	84	+ AVIO_DATA_MARKER_UNKNOWN,
	85	+ /**
	86	+ * Trailer data, which doesn't contain actual content, but only for
	87	+ * finalizing the output file.
	88	+ */
	89	+ AVIO_DATA_MARKER_TRAILER
	90	+};
	91	+
56	92	/**
57	93	* Bytestream IO Context.
58	94	* New fields can be added to the end with minor version bumps.
@@ -115,6 +151,24 @@ typedef struct AVIOContext { · 56 unmodified lines
115	151	* A combination of AVIO_SEEKABLE_ flags or 0 when the stream is not seekable.
116	152	*/
117	153	int seekable;
	154	+
	155	+ /**
	156	+ * A callback that is used instead of write_packet.
	157	+ */
	158	+ int (write_data_type)(void opaque, uint8_t *buf, int buf_size,
	159	+ enum AVIODataMarkerType type, int64_t time);
	160	+ /**
	161	+ * If set, don't call write_data_type separately for AVIO_DATA_MARKER_BOUNDARY_POINT,
	162	+ * but ignore them and treat them as AVIO_DATA_MARKER_UNKNOWN (to avoid needlessly
	163	+ * small chunks of data returned from the callback).
	164	+ */
	165	+ int ignore_boundary_point;
	166	+
	167	+ /**
	168	+ * Internal, not meant to be used from outside of AVIOContext.
	169	+ */
	170	+ enum AVIODataMarkerType current_type;
	171	+ int64_t last_time;
118	172	} AVIOContext;
119	173
120	174	/**
@@ -192,6 +246,18 @@ int avio_put_str16le(AVIOContext s, const char str); · 71 unmodified lines
192	246	*/
193	247	int avio_put_str16be(AVIOContext s, const char str);
194	248
	249	+/**
	250	+ * Mark the written bytestream as a specific type.
	251	+ *
	252	+ * Zero-length ranges are omitted from the output.
	253	+ *
	254	+ * @param time the stream time the current bytestream pos corresponds to
	255	+ * (in AV_TIME_BASE units), or AV_NOPTS_VALUE if unknown or not
	256	+ * applicable
	257	+ * @param type the kind of data written starting at the current pos
	258	+ */
	259	+void avio_write_marker(AVIOContext *s, int64_t time, enum AVIODataMarkerType type);
	260	+
195	261	/**
196	262	* ORing this as the "whence" parameter to a seek function causes it to
197	263	* return the filesize without seeking anywhere. Supporting this is optional.

libavformat/aviobuf.c+50−2

@@ -140,6 +140,11 @@ int ffio_init_context(AVIOContext *s, · 139 unmodified lines
140	140	s->read_pause = NULL;
141	141	s->read_seek = NULL;
142	142
	143	+ s->write_data_type = NULL;
	144	+ s->ignore_boundary_point = 0;
	145	+ s->current_type = AVIO_DATA_MARKER_UNKNOWN;
	146	+ s->last_time = AV_NOPTS_VALUE;
	147	+
143	148	return 0;
144	149	}
145	150
@@ -163,13 +168,25 @@ AVIOContext *avio_alloc_context( · 17 unmodified lines
163	168	static void flush_buffer(AVIOContext *s)
164	169	{
165	170	if (s->buf_ptr > s->buffer) {
166		− if (s->write_packet && !s->error) {
167		− int ret = s->write_packet(s->opaque, s->buffer,
	171	+ if (!s->error) {
	172	+ int ret = 0;
	173	+ if (s->write_data_type)
	174	+ ret = s->write_data_type(s->opaque, s->buffer,
	175	+ s->buf_ptr - s->buffer,
	176	+ s->current_type,
	177	+ s->last_time);
	178	+ else if (s->write_packet)
	179	+ ret = s->write_packet(s->opaque, s->buffer,
168	180	s->buf_ptr - s->buffer);
169	181	if (ret < 0) {
170	182	s->error = ret;
171	183	}
172	184	}
	185	+ if (s->current_type == AVIO_DATA_MARKER_SYNC_POINT \|\|
	186	+ s->current_type == AVIO_DATA_MARKER_BOUNDARY_POINT) {
	187	+ s->current_type = AVIO_DATA_MARKER_UNKNOWN;
	188	+ }
	189	+ s->last_time = AV_NOPTS_VALUE;
173	190	if (s->update_checksum) {
174	191	s->checksum = s->update_checksum(s->checksum, s->checksum_ptr,
175	192	s->buf_ptr - s->checksum_ptr);
@@ -402,6 +419,37 @@ void avio_wb24(AVIOContext *s, unsigned int val) · 226 unmodified lines
402	419	avio_w8(s, val);
403	420	}
404	421
	422	+void avio_write_marker(AVIOContext *s, int64_t time, enum AVIODataMarkerType type)
	423	+{
	424	+ if (!s->write_data_type)
	425	+ return;
	426	+ // If ignoring boundary points, just treat it as unknown
	427	+ if (type == AVIO_DATA_MARKER_BOUNDARY_POINT && s->ignore_boundary_point)
	428	+ type = AVIO_DATA_MARKER_UNKNOWN;
	429	+ // Avoid unnecessary flushes if we are already in non-header/trailer
	430	+ // data and setting the type to unknown
	431	+ if (type == AVIO_DATA_MARKER_UNKNOWN &&
	432	+ (s->current_type != AVIO_DATA_MARKER_HEADER &&
	433	+ s->current_type != AVIO_DATA_MARKER_TRAILER))
	434	+ return;
	435	+
	436	+ switch (type) {
	437	+ case AVIO_DATA_MARKER_HEADER:
	438	+ case AVIO_DATA_MARKER_TRAILER:
	439	+ // For header/trailer, ignore a new marker of the same type;
	440	+ // consecutive header/trailer markers can be merged.
	441	+ if (type == s->current_type)
	442	+ return;
	443	+ break;
	444	+ }
	445	+
	446	+ // If we've reached here, we have a new, noteworthy marker.
	447	+ // Flush the previous data and mark the start of the new data.
	448	+ avio_flush(s);
	449	+ s->current_type = type;
	450	+ s->last_time = time;
	451	+}
	452	+
405	453	/* Input stream */
406	454
407	455	static void fill_buffer(AVIOContext *s)

libavformat/mux.c+6−0

@@ -256,11 +256,15 @@ int avformat_write_header(AVFormatContext s, AVDictionary *options) · 255 unmodified lines
256	256	if (ret = init_muxer(s, options))
257	257	return ret;
258	258
	259	+ if (!(s->oformat->flags & AVFMT_NOFILE) && s->pb)
	260	+ avio_write_marker(s->pb, AV_NOPTS_VALUE, AVIO_DATA_MARKER_HEADER);
259	261	if (s->oformat->write_header) {
260	262	ret = s->oformat->write_header(s);
261	263	if (ret < 0)
262	264	return ret;
263	265	}
	266	+ if (!(s->oformat->flags & AVFMT_NOFILE) && s->pb)
	267	+ avio_write_marker(s->pb, AV_NOPTS_VALUE, AVIO_DATA_MARKER_UNKNOWN);
264	268
265	269	if (s->avoid_negative_ts == AVFMT_AVOID_NEG_TS_AUTO) {
266	270	if (s->oformat->flags & (AVFMT_TS_NEGATIVE \| AVFMT_NOTIMESTAMPS)) {
@@ -704,6 +708,8 @@ int av_write_trailer(AVFormatContext *s) · 437 unmodified lines
704	708	goto fail;
705	709	}
706	710
	711	+ if (!(s->oformat->flags & AVFMT_NOFILE) && s->pb)
	712	+ avio_write_marker(s->pb, AV_NOPTS_VALUE, AVIO_DATA_MARKER_TRAILER);
707	713	if (s->oformat->write_trailer)
708	714	ret = s->oformat->write_trailer(s);
709	715

libavformat/version.h+1−1

@@ -30,7 +30,7 @@ · 29 unmodified lines
30	30	#include "libavutil/version.h"
31	31
32	32	#define LIBAVFORMAT_VERSION_MAJOR 57
33		−#define LIBAVFORMAT_VERSION_MINOR 6
	33	+#define LIBAVFORMAT_VERSION_MINOR 7
34	34	#define LIBAVFORMAT_VERSION_MICRO 0
35	35
36	36	#define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \

avio: Allow custom IO users to get labels for the output bytestream

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