Add AVIO_FLAG_DIRECT.

Allows avoiding the buffer when using avio read, write and seek functions.
When using the ffmpeg executable -avioflags direct can be used to enable
this mode for input files, but has no effect on output files.
Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

libavformat/avformat.h

@@ -1083,6 +1083,8 @@ typedef struct AVFormatContext {
      */
 #define RAW_PACKET_BUFFER_SIZE 2500000
     int raw_packet_buffer_remaining_size;
+
+    int avio_flags;
 } AVFormatContext;
 
 typedef struct AVPacketList {

libavformat/avio.h

@@ -121,6 +121,13 @@ typedef struct {
      * This field is internal to libavformat and access from outside is not allowed.
      */
      int64_t maxsize;
+
+     /**
+      * avio_read and avio_write should if possible be satisfied directly
+      * instead of going through a buffer, and avio_seek will always
+      * call the underlying seek function directly.
+      */
+     int direct;
 } AVIOContext;
 
 /* unbuffered I/O */
@@ -319,6 +326,14 @@ int avio_get_str16be(AVIOContext *pb, int maxlen, char *buf, int buflen);
  */
 #define AVIO_FLAG_NONBLOCK 8
 
+/**
+ * Use direct mode.
+ * avio_read and avio_write should if possible be satisfied directly
+ * instead of going through a buffer, and avio_seek will always
+ * call the underlying seek function directly.
+ */
+#define AVIO_FLAG_DIRECT 0x8000
+
 /**
  * Create and initialize a AVIOContext for accessing the
  * resource indicated by url.

libavformat/aviobuf.c

@@ -80,6 +80,7 @@ int ffio_init_context(AVIOContext *s,
     s->buffer_size = buffer_size;
     s->buf_ptr = buffer;
     s->opaque = opaque;
+    s->direct = 0;
     url_resetbuf(s, write_flag ? AVIO_FLAG_WRITE : AVIO_FLAG_READ);
     s->write_packet = write_packet;
     s->read_packet = read_packet;
@@ -117,20 +118,25 @@ AVIOContext *avio_alloc_context(
     return s;
 }
 
-static void flush_buffer(AVIOContext *s)
+static void writeout(AVIOContext *s, const uint8_t *data, int len)
 {
-    if (s->buf_ptr > s->buffer) {
     if (s->write_packet && !s->error){
-            int ret= s->write_packet(s->opaque, s->buffer, s->buf_ptr - s->buffer);
+        int ret= s->write_packet(s->opaque, data, len);
         if(ret < 0){
             s->error = ret;
         }
     }
+    s->pos += len;
+}
+
+static void flush_buffer(AVIOContext *s)
+{
+    if (s->buf_ptr > s->buffer) {
+        writeout(s, s->buffer, s->buf_ptr - s->buffer);
         if(s->update_checksum){
             s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_ptr - s->checksum_ptr);
             s->checksum_ptr= s->buffer;
         }
-        s->pos += s->buf_ptr - s->buffer;
     }
     s->buf_ptr = s->buffer;
 }
@@ -158,6 +164,11 @@ void ffio_fill(AVIOContext *s, int b, int count)
 
 void avio_write(AVIOContext *s, const unsigned char *buf, int size)
 {
+    if (s->direct && !s->update_checksum) {
+        avio_flush(s);
+        writeout(s, buf, size);
+        return;
+    }
     while (size > 0) {
         int len = FFMIN(s->buf_end - s->buf_ptr, size);
         memcpy(s->buf_ptr, buf, len);
@@ -199,13 +210,14 @@ int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
         offset += offset1;
     }
     offset1 = offset - pos;
-    if (!s->must_flush &&
+    if (!s->must_flush && (!s->direct || !s->seek) &&
         offset1 >= 0 && offset1 <= (s->buf_end - s->buffer)) {
         /* can do the seek inside the buffer */
         s->buf_ptr = s->buffer + offset1;
     } else if ((!s->seekable ||
                offset1 <= s->buf_end + SHORT_SEEK_THRESHOLD - s->buffer) &&
                !s->write_flag && offset1 >= 0 &&
+               (!s->direct || !s->seek) &&
               (whence != SEEK_END || force)) {
         while(s->pos < offset && !s->eof_reached)
             fill_buffer(s);
@@ -458,7 +470,7 @@ int avio_read(AVIOContext *s, unsigned char *buf, int size)
         if (len > size)
             len = size;
         if (len == 0) {
-            if(size > s->buffer_size && !s->update_checksum){
+            if((s->direct || size > s->buffer_size) && !s->update_checksum){
                 if(s->read_packet)
                     len = s->read_packet(s->opaque, buf, size);
                 if (len <= 0) {
@@ -670,6 +682,7 @@ int ffio_fdopen(AVIOContext **s, URLContext *h)
         av_free(buffer);
         return AVERROR(ENOMEM);
     }
+    (*s)->direct = h->flags & AVIO_FLAG_DIRECT;
     (*s)->seekable = h->is_streamed ? 0 : AVIO_SEEKABLE_NORMAL;
     (*s)->max_packet_size = max_packet_size;
     if(h->prot) {

libavformat/options_table.h

@@ -28,6 +28,8 @@
 #define D AV_OPT_FLAG_DECODING_PARAM
 
 static const AVOption options[]={
+{"avioflags", NULL, OFFSET(avio_flags), AV_OPT_TYPE_FLAGS, {.dbl = DEFAULT }, INT_MIN, INT_MAX, D|E, "avioflags"},
+{"direct", "reduce buffering", 0, AV_OPT_TYPE_CONST, {.dbl = AVIO_FLAG_DIRECT }, INT_MIN, INT_MAX, D|E, "avioflags"},
 {"probesize", "set probing size", OFFSET(probesize), AV_OPT_TYPE_INT, {.dbl = 5000000 }, 32, INT_MAX, D},
 {"packetsize", "set packet size", OFFSET(packet_size), AV_OPT_TYPE_INT, {.dbl = DEFAULT }, 0, INT_MAX, E},
 {"fflags", NULL, OFFSET(flags), AV_OPT_TYPE_FLAGS, {.dbl = DEFAULT }, INT_MIN, INT_MAX, D|E, "fflags"},

libavformat/utils.c

@@ -543,7 +543,7 @@ static int init_input(AVFormatContext *s, const char *filename, AVDictionary **o
         (!s->iformat && (s->iformat = av_probe_input_format(&pd, 0))))
         return 0;
 
-    if ((ret = avio_open2(&s->pb, filename, AVIO_FLAG_READ,
+    if ((ret = avio_open2(&s->pb, filename, AVIO_FLAG_READ | s->avio_flags,
                           &s->interrupt_callback, options)) < 0)
         return ret;
     if (s->iformat)

tests/fate/demux.mak

+FATE_DEMUX += fate-avio-direct
+fate-avio-direct: CMD = framecrc -avioflags direct -i $(SAMPLES)/fraps/fraps-v5-bouncing-balls-partial.avi -avioflags direct
+
 FATE_DEMUX += fate-adts-demux
 fate-adts-demux: CMD = crc -i $(SAMPLES)/aac/ct_faac-adts.aac -acodec copy