lavf: add subfile protocol.

Changelog

@@ -32,6 +32,7 @@ version 2.2:
 - Support DNx444
 - libx265 encoder
 - dejudder filter
+- subfile protocol
 
 
 version 2.1:

doc/protocols.texi

@@ -951,6 +951,30 @@ this binary block are used as master key, the following 14 bytes are
 used as master salt.
 @end table
 
+@section subfile
+
+Virtually extract a segment of a file or another stream.
+The underlying stream must be seekable.
+
+Accepted options:
+@table @option
+@item start
+Start offset of the extracted segment, in bytes.
+@item end
+End offset of the extracted segment, in bytes.
+@end table
+
+Examples:
+
+Extract a chapter from a DVD VOB file (start and end sectors obtained
+externally and multiplied by 2048):
+@example
+subfile,,start,153391104,end,268142592,,:/media/dvd/VIDEO_TS/VTS_08_1.VOB
+@end example
+
+Play an AVI file directly from a TAR archive:
+subfile,,start,183241728,end,366490624,,:archive.tar
+
 @section tcp
 
 Transmission Control Protocol.

libavformat/Makefile

@@ -464,6 +464,7 @@ OBJS-$(CONFIG_RTMPTS_PROTOCOL)           += rtmpproto.o rtmppkt.o
 OBJS-$(CONFIG_RTP_PROTOCOL)              += rtpproto.o
 OBJS-$(CONFIG_SCTP_PROTOCOL)             += sctp.o
 OBJS-$(CONFIG_SRTP_PROTOCOL)             += srtpproto.o srtp.o
+OBJS-$(CONFIG_SUBFILE_PROTOCOL)          += subfile.o
 OBJS-$(CONFIG_TCP_PROTOCOL)              += tcp.o
 OBJS-$(CONFIG_TLS_PROTOCOL)              += tls.o
 OBJS-$(CONFIG_UDP_PROTOCOL)              += udp.o

libavformat/allformats.c

@@ -338,6 +338,7 @@ void av_register_all(void)
     REGISTER_PROTOCOL(RTP,              rtp);
     REGISTER_PROTOCOL(SCTP,             sctp);
     REGISTER_PROTOCOL(SRTP,             srtp);
+    REGISTER_PROTOCOL(SUBFILE,          subfile);
     REGISTER_PROTOCOL(TCP,              tcp);
     REGISTER_PROTOCOL(TLS,              tls);
     REGISTER_PROTOCOL(UDP,              udp);

libavformat/subfile.c

+/*
+ * Copyright (c) 2014 Nicolas George
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/avstring.h"
+#include "libavutil/opt.h"
+#include "avformat.h"
+#include "url.h"
+
+typedef struct SubfileContext {
+    const AVClass *class;
+    URLContext *h;
+    int64_t start;
+    int64_t end;
+    int64_t pos;
+} SubfileContext;
+
+#define OFFSET(field) offsetof(SubfileContext, field)
+#define D AV_OPT_FLAG_DECODING_PARAM
+
+static const AVOption subfile_options[] = {
+    { "start", "start offset", OFFSET(start), AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
+    { "end",   "end offset",   OFFSET(end),   AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
+    { NULL }
+};
+
+#undef OFFSET
+#undef D
+
+static const AVClass subfile_class = {
+    .class_name = "subfile",
+    .item_name  = av_default_item_name,
+    .option     = subfile_options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+static int slave_seek(URLContext *h)
+{
+    SubfileContext *c = h->priv_data;
+    int64_t ret;
+
+    if ((ret = ffurl_seek(c->h, c->pos, SEEK_SET)) != c->pos) {
+        if (ret >= 0)
+            ret = AVERROR_BUG;
+        av_log(h, AV_LOG_ERROR, "Impossible to seek in file: %s\n",
+               av_err2str(ret));
+        return ret;
+    }
+    return 0;
+}
+
+static int subfile_open(URLContext *h, const char *filename, int flags,
+                        AVDictionary **options)
+{
+    SubfileContext *c = h->priv_data;
+    int ret;
+
+    if (c->end <= c->start) {
+        av_log(h, AV_LOG_ERROR, "end before start\n");
+        return AVERROR(EINVAL);
+    }
+    av_strstart(filename, "subfile:", &filename);
+    ret = ffurl_open(&c->h, filename, flags, &h->interrupt_callback, options);
+    if (ret < 0)
+        return ret;
+    c->pos = c->start;
+    if ((ret = slave_seek(h)) < 0) {
+        ffurl_close(c->h);
+        return ret;
+    }
+    return 0;
+}
+
+static int subfile_close(URLContext *h)
+{
+    SubfileContext *c = h->priv_data;
+    return ffurl_close(c->h);
+}
+
+static int subfile_read(URLContext *h, unsigned char *buf, int size)
+{
+    SubfileContext *c = h->priv_data;
+    int64_t rest = c->end - c->pos;
+    int ret;
+
+    if (rest <= 0)
+        return 0;
+    size = FFMIN(size, rest);
+    ret = ffurl_read(c->h, buf, size);
+    if (ret >= 0)
+        c->pos += ret;
+    return ret;
+}
+
+static int64_t subfile_seek(URLContext *h, int64_t pos, int whence)
+{
+    SubfileContext *c = h->priv_data;
+    int64_t new_pos = -1;
+    int ret;
+
+    if (whence == AVSEEK_SIZE)
+        return c->end - c->start;
+    switch (whence) {
+    case SEEK_SET:
+        new_pos = c->start + pos;
+        break;
+    case SEEK_CUR:
+        new_pos += pos;
+        break;
+    case SEEK_END:
+        new_pos = c->end + c->pos;
+        break;
+    }
+    if (new_pos < c->start)
+        return AVERROR(EINVAL);
+    c->pos = new_pos;
+    if ((ret = slave_seek(h)) < 0)
+        return ret;
+    return c->pos - c->start;
+}
+
+URLProtocol ff_subfile_protocol = {
+    .name                = "subfile",
+    .url_open2           = subfile_open,
+    .url_read            = subfile_read,
+    .url_seek            = subfile_seek,
+    .url_close           = subfile_close,
+    .priv_data_size      = sizeof(SubfileContext),
+    .priv_data_class     = &subfile_class,
+};

libavformat/version.h

@@ -30,8 +30,8 @@
 #include "libavutil/version.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 55
-#define LIBAVFORMAT_VERSION_MINOR 33
-#define LIBAVFORMAT_VERSION_MICRO 101
+#define LIBAVFORMAT_VERSION_MINOR 34
+#define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \