Moved from gst-plugins/ext/mplex/. See that directory for older changelogs.

Original commit message from CVS:
Moved from gst-plugins/ext/mplex/.  See that directory for older
changelogs.

1 files changed, 880 insertions, 0 deletions

diff --git a/gst-libs/ext/mplex/yuv4mpeg.cc b/gst-libs/ext/mplex/yuv4mpeg.cc
new file mode 100644
index 00000000..a9e1aebf
--- /dev/null
+++ b/gst-libs/ext/mplex/yuv4mpeg.cc
@@ -0,0 +1,880 @@
+/*
+ *  yuv4mpeg.c:  Functions for reading and writing "new" YUV4MPEG streams
+ *
+ *  Copyright (C) 2001 Matthew J. Marjanovic <maddog@mir.com>
+ *
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version 2
+ *  of the License, or (at your option) any later version.
+ *
+ *  This program 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ *
+ */
+
+#include <config.h>
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "yuv4mpeg.h"
+#include "yuv4mpeg_intern.h"
+#include "mjpeg_logging.h"
+
+
+static int _y4mparam_allow_unknown_tags = 1;	/* default is forgiveness */
+
+static void *(*_y4m_alloc) (size_t bytes) = malloc;
+static void (*_y4m_free) (void *ptr) = free;
+
+
+
+int
+y4m_allow_unknown_tags (int yn)
+{
+  int old = _y4mparam_allow_unknown_tags;
+
+  if (yn >= 0)
+    _y4mparam_allow_unknown_tags = (yn) ? 1 : 0;
+  return old;
+}
+
+
+
+/*************************************************************************
+ *
+ * Convenience functions for fd read/write
+ *
+ *   - guaranteed to transfer entire payload (or fail)
+ *   - returns:
+ *               0 on complete success
+ *               +(# of remaining bytes) on eof (for y4m_read)
+ *               -(# of rem. bytes) on error (and ERRNO should be set)
+ *     
+ *************************************************************************/
+
+
+ssize_t
+y4m_read (int fd, void *buf, size_t len)
+{
+  ssize_t n;
+  uint8_t *ptr = (uint8_t *) buf;
+
+  while (len > 0) {
+    n = read (fd, ptr, len);
+    if (n <= 0) {
+      /* return amount left to read */
+      if (n == 0)
+	return len;		/* n == 0 --> eof */
+      else
+	return -len;		/* n < 0 --> error */
+    }
+    ptr += n;
+    len -= n;
+  }
+  return 0;
+}
+
+
+ssize_t
+y4m_write (int fd, const void *buf, size_t len)
+{
+  ssize_t n;
+  const uint8_t *ptr = (const uint8_t *) buf;
+
+  while (len > 0) {
+    n = write (fd, ptr, len);
+    if (n <= 0)
+      return -len;		/* return amount left to write */
+    ptr += n;
+    len -= n;
+  }
+  return 0;
+}
+
+
+
+/*************************************************************************
+ *
+ * "Extra tags" handling
+ *
+ *************************************************************************/
+
+
+static char *
+y4m_new_xtag (void)
+{
+  return (char *) _y4m_alloc (Y4M_MAX_XTAG_SIZE * sizeof (char));
+}
+
+
+void
+y4m_init_xtag_list (y4m_xtag_list_t * xtags)
+{
+  int i;
+
+  xtags->count = 0;
+  for (i = 0; i < Y4M_MAX_XTAGS; i++) {
+    xtags->tags[i] = NULL;
+  }
+}
+
+
+void
+y4m_fini_xtag_list (y4m_xtag_list_t * xtags)
+{
+  int i;
+
+  for (i = 0; i < Y4M_MAX_XTAGS; i++) {
+    if (xtags->tags[i] != NULL) {
+      _y4m_free (xtags->tags[i]);
+      xtags->tags[i] = NULL;
+    }
+  }
+  xtags->count = 0;
+}
+
+
+void
+y4m_copy_xtag_list (y4m_xtag_list_t * dest, const y4m_xtag_list_t * src)
+{
+  int i;
+
+  for (i = 0; i < src->count; i++) {
+    if (dest->tags[i] == NULL)
+      dest->tags[i] = y4m_new_xtag ();
+    strncpy (dest->tags[i], src->tags[i], Y4M_MAX_XTAG_SIZE);
+  }
+  dest->count = src->count;
+}
+
+
+
+static int
+y4m_snprint_xtags (char *s, int maxn, const y4m_xtag_list_t * xtags)
+{
+  int i, room;
+
+  for (i = 0, room = maxn - 1; i < xtags->count; i++) {
+    int n = snprintf (s, room + 1, " %s", xtags->tags[i]);
+
+    if ((n < 0) || (n > room))
+      return Y4M_ERR_HEADER;
+    s += n;
+    room -= n;
+  }
+  s[0] = '\n';			/* finish off header with newline */
+  s[1] = '\0';			/* ...and end-of-string           */
+  return Y4M_OK;
+}
+
+
+int
+y4m_xtag_count (const y4m_xtag_list_t * xtags)
+{
+  return xtags->count;
+}
+
+
+const char *
+y4m_xtag_get (const y4m_xtag_list_t * xtags, int n)
+{
+  if (n >= xtags->count)
+    return NULL;
+  else
+    return xtags->tags[n];
+}
+
+
+int
+y4m_xtag_add (y4m_xtag_list_t * xtags, const char *tag)
+{
+  if (xtags->count >= Y4M_MAX_XTAGS)
+    return Y4M_ERR_XXTAGS;
+  if (xtags->tags[xtags->count] == NULL)
+    xtags->tags[xtags->count] = y4m_new_xtag ();
+  strncpy (xtags->tags[xtags->count], tag, Y4M_MAX_XTAG_SIZE);
+  (xtags->count)++;
+  return Y4M_OK;
+}
+
+
+int
+y4m_xtag_remove (y4m_xtag_list_t * xtags, int n)
+{
+  int i;
+  char *q;
+
+  if ((n < 0) || (n >= xtags->count))
+    return Y4M_ERR_RANGE;
+  q = xtags->tags[n];
+  for (i = n; i < (xtags->count - 1); i++)
+    xtags->tags[i] = xtags->tags[i + 1];
+  xtags->tags[i] = q;
+  (xtags->count)--;
+  return Y4M_OK;
+}
+
+
+int
+y4m_xtag_clearlist (y4m_xtag_list_t * xtags)
+{
+  xtags->count = 0;
+  return Y4M_OK;
+}
+
+
+int
+y4m_xtag_addlist (y4m_xtag_list_t * dest, const y4m_xtag_list_t * src)
+{
+  int i, j;
+
+  if ((dest->count + src->count) > Y4M_MAX_XTAGS)
+    return Y4M_ERR_XXTAGS;
+  for (i = dest->count, j = 0; j < src->count; i++, j++) {
+    if (dest->tags[i] == NULL)
+      dest->tags[i] = y4m_new_xtag ();
+    strncpy (dest->tags[i], src->tags[i], Y4M_MAX_XTAG_SIZE);
+  }
+  dest->count += src->count;
+  return Y4M_OK;
+}
+
+
+/*************************************************************************
+ *
+ * Creators/destructors for y4m_*_info_t structures
+ *
+ *************************************************************************/
+
+
+void
+y4m_init_stream_info (y4m_stream_info_t * info)
+{
+  if (info == NULL)
+    return;
+  /* initialize info */
+  info->width = Y4M_UNKNOWN;
+  info->height = Y4M_UNKNOWN;
+  info->interlace = Y4M_UNKNOWN;
+  info->framerate = y4m_fps_UNKNOWN;
+  info->sampleaspect = y4m_sar_UNKNOWN;
+  y4m_init_xtag_list (&(info->x_tags));
+}
+
+
+void
+y4m_copy_stream_info (y4m_stream_info_t * dest, const y4m_stream_info_t * src)
+{
+  if ((dest == NULL) || (src == NULL))
+    return;
+  /* copy info */
+  dest->width = src->width;
+  dest->height = src->height;
+  dest->interlace = src->interlace;
+  dest->framerate = src->framerate;
+  dest->sampleaspect = src->sampleaspect;
+  dest->framelength = src->framelength;
+  y4m_copy_xtag_list (&(dest->x_tags), &(src->x_tags));
+}
+
+
+void
+y4m_fini_stream_info (y4m_stream_info_t * info)
+{
+  if (info == NULL)
+    return;
+  y4m_fini_xtag_list (&(info->x_tags));
+}
+
+
+void
+y4m_si_set_width (y4m_stream_info_t * si, int width)
+{
+  si->width = width;
+  si->framelength = (si->height * si->width) * 3 / 2;
+}
+
+int
+y4m_si_get_width (const y4m_stream_info_t * si)
+{
+  return si->width;
+}
+
+void
+y4m_si_set_height (y4m_stream_info_t * si, int height)
+{
+  si->height = height;
+  si->framelength = (si->height * si->width) * 3 / 2;
+}
+
+int
+y4m_si_get_height (const y4m_stream_info_t * si)
+{
+  return si->height;
+}
+
+void
+y4m_si_set_interlace (y4m_stream_info_t * si, int interlace)
+{
+  si->interlace = interlace;
+}
+
+int
+y4m_si_get_interlace (const y4m_stream_info_t * si)
+{
+  return si->interlace;
+}
+
+void
+y4m_si_set_framerate (y4m_stream_info_t * si, y4m_ratio_t framerate)
+{
+  si->framerate = framerate;
+}
+
+y4m_ratio_t
+y4m_si_get_framerate (const y4m_stream_info_t * si)
+{
+  return si->framerate;
+}
+
+void
+y4m_si_set_sampleaspect (y4m_stream_info_t * si, y4m_ratio_t sar)
+{
+  si->sampleaspect = sar;
+}
+
+y4m_ratio_t
+y4m_si_get_sampleaspect (const y4m_stream_info_t * si)
+{
+  return si->sampleaspect;
+}
+
+int
+y4m_si_get_framelength (const y4m_stream_info_t * si)
+{
+  return si->framelength;
+}
+
+y4m_xtag_list_t *
+y4m_si_xtags (y4m_stream_info_t * si)
+{
+  return &(si->x_tags);
+}
+
+
+
+void
+y4m_init_frame_info (y4m_frame_info_t * info)
+{
+  if (info == NULL)
+    return;
+  /* initialize info */
+  y4m_init_xtag_list (&(info->x_tags));
+}
+
+
+void
+y4m_copy_frame_info (y4m_frame_info_t * dest, const y4m_frame_info_t * src)
+{
+  if ((dest == NULL) || (src == NULL))
+    return;
+  /* copy info */
+  y4m_copy_xtag_list (&(dest->x_tags), &(src->x_tags));
+}
+
+
+void
+y4m_fini_frame_info (y4m_frame_info_t * info)
+{
+  if (info == NULL)
+    return;
+  y4m_fini_xtag_list (&(info->x_tags));
+}
+
+
+
+/*************************************************************************
+ *
+ * Tag parsing 
+ *
+ *************************************************************************/
+
+int
+y4m_parse_stream_tags (char *s, y4m_stream_info_t * i)
+{
+  char *token, *value;
+  char tag;
+  int err;
+
+  /* parse fields */
+  for (token = strtok (s, Y4M_DELIM); token != NULL; token = strtok (NULL, Y4M_DELIM)) {
+    if (token[0] == '\0')
+      continue;			/* skip empty strings */
+    tag = token[0];
+    value = token + 1;
+    switch (tag) {
+      case 'W':		/* width */
+	i->width = atoi (value);
+	if (i->width <= 0)
+	  return Y4M_ERR_RANGE;
+	break;
+      case 'H':		/* height */
+	i->height = atoi (value);
+	if (i->height <= 0)
+	  return Y4M_ERR_RANGE;
+	break;
+      case 'F':		/* frame rate (fps) */
+	if ((err = y4m_parse_ratio (&(i->framerate), value)) != Y4M_OK)
+	  return err;
+	if (i->framerate.n < 0)
+	  return Y4M_ERR_RANGE;
+	break;
+      case 'I':		/* interlacing */
+	switch (value[0]) {
+	  case 'p':
+	    i->interlace = Y4M_ILACE_NONE;
+	    break;
+	  case 't':
+	    i->interlace = Y4M_ILACE_TOP_FIRST;
+	    break;
+	  case 'b':
+	    i->interlace = Y4M_ILACE_BOTTOM_FIRST;
+	    break;
+	  case '?':
+	  default:
+	    i->interlace = Y4M_UNKNOWN;
+	    break;
+	}
+	break;
+      case 'A':		/* sample (pixel) aspect ratio */
+	if ((err = y4m_parse_ratio (&(i->sampleaspect), value)) != Y4M_OK)
+	  return err;
+	if (i->sampleaspect.n < 0)
+	  return Y4M_ERR_RANGE;
+	break;
+      case 'X':		/* 'X' meta-tag */
+	if ((err = y4m_xtag_add (&(i->x_tags), token)) != Y4M_OK)
+	  return err;
+	break;
+      default:
+	/* possible error on unknown options */
+	if (_y4mparam_allow_unknown_tags) {
+	  /* unknown tags ok:  store in xtag list and warn... */
+	  if ((err = y4m_xtag_add (&(i->x_tags), token)) != Y4M_OK)
+	    return err;
+	  mjpeg_warn ("Unknown stream tag encountered:  '%s'", token);
+	} else {
+	  /* unknown tags are *not* ok */
+	  return Y4M_ERR_BADTAG;
+	}
+	break;
+    }
+  }
+  /* Error checking... width and height must be known since we can't
+   * parse without them
+   */
+  if (i->width == Y4M_UNKNOWN || i->height == Y4M_UNKNOWN)
+    return Y4M_ERR_HEADER;
+  /* ta da!  done. */
+  return Y4M_OK;
+}
+
+
+
+static int
+y4m_parse_frame_tags (char *s, y4m_frame_info_t * i)
+{
+  char *token, *value;
+  char tag;
+  int err;
+
+  /* parse fields */
+  for (token = strtok (s, Y4M_DELIM); token != NULL; token = strtok (NULL, Y4M_DELIM)) {
+    if (token[0] == '\0')
+      continue;			/* skip empty strings */
+    tag = token[0];
+    value = token + 1;
+    switch (tag) {
+      case 'X':		/* 'X' meta-tag */
+	if ((err = y4m_xtag_add (&(i->x_tags), token)) != Y4M_OK)
+	  return err;
+	break;
+      default:
+	/* possible error on unknown options */
+	if (_y4mparam_allow_unknown_tags) {
+	  /* unknown tags ok:  store in xtag list and warn... */
+	  if ((err = y4m_xtag_add (&(i->x_tags), token)) != Y4M_OK)
+	    return err;
+	  mjpeg_warn ("Unknown frame tag encountered:  '%s'", token);
+	} else {
+	  /* unknown tags are *not* ok */
+	  return Y4M_ERR_BADTAG;
+	}
+	break;
+    }
+  }
+  /* ta da!  done. */
+  return Y4M_OK;
+}
+
+
+
+
+
+/*************************************************************************
+ *
+ * Read/Write stream header
+ *
+ *************************************************************************/
+
+
+int
+y4m_read_stream_header (int fd, y4m_stream_info_t * i)
+{
+  char line[Y4M_LINE_MAX];
+  char *p;
+  int n;
+  int err;
+
+  /* read the header line */
+  for (n = 0, p = line; n < Y4M_LINE_MAX; n++, p++) {
+    if (read (fd, p, 1) < 1)
+      return Y4M_ERR_SYSTEM;
+    if (*p == '\n') {
+      *p = '\0';		/* Replace linefeed by end of string */
+      break;
+    }
+  }
+  if (n >= Y4M_LINE_MAX)
+    return Y4M_ERR_HEADER;
+  /* look for keyword in header */
+  if (strncmp (line, Y4M_MAGIC, strlen (Y4M_MAGIC)))
+    return Y4M_ERR_MAGIC;
+  if ((err = y4m_parse_stream_tags (line + strlen (Y4M_MAGIC), i)) != Y4M_OK)
+    return err;
+
+  i->framelength = (i->height * i->width) * 3 / 2;
+  return Y4M_OK;
+}
+
+
+
+int
+y4m_write_stream_header (int fd, const y4m_stream_info_t * i)
+{
+  char s[Y4M_LINE_MAX + 1];
+  int n;
+  int err;
+  y4m_ratio_t rate = i->framerate;
+  y4m_ratio_t aspect = i->sampleaspect;
+
+  y4m_ratio_reduce (&rate);
+  y4m_ratio_reduce (&aspect);
+  n = snprintf (s, sizeof (s), "%s W%d H%d F%d:%d I%s A%d:%d",
+		Y4M_MAGIC,
+		i->width,
+		i->height,
+		rate.n, rate.d,
+		(i->interlace == Y4M_ILACE_NONE) ? "p" :
+		(i->interlace == Y4M_ILACE_TOP_FIRST) ? "t" :
+		(i->interlace == Y4M_ILACE_BOTTOM_FIRST) ? "b" : "?", aspect.n, aspect.d);
+  if ((n < 0) || (n > Y4M_LINE_MAX))
+    return Y4M_ERR_HEADER;
+  if ((err = y4m_snprint_xtags (s + n, sizeof (s) - n - 1, &(i->x_tags)))
+      != Y4M_OK)
+    return err;
+  /* non-zero on error */
+  return (y4m_write (fd, s, strlen (s)) ? Y4M_ERR_SYSTEM : Y4M_OK);
+}
+
+
+
+
+
+/*************************************************************************
+ *
+ * Read/Write frame header
+ *
+ *************************************************************************/
+
+int
+y4m_read_frame_header (int fd, y4m_frame_info_t * i)
+{
+  char line[Y4M_LINE_MAX];
+  char *p;
+  int n;
+  ssize_t remain;
+
+  /* This is more clever than read_stream_header...
+     Try to read "FRAME\n" all at once, and don't try to parse
+     if nothing else is there...
+   */
+  remain = y4m_read (fd, line, sizeof (Y4M_FRAME_MAGIC) - 1 + 1);	/* -'\0', +'\n' */
+  if (remain < 0)
+    return Y4M_ERR_SYSTEM;
+  if (remain > 0) {
+    /* A clean EOF should end exactly at a frame-boundary */
+    if (remain == sizeof (Y4M_FRAME_MAGIC))
+      return Y4M_ERR_EOF;
+    else
+      return Y4M_ERR_BADEOF;
+  }
+  if (strncmp (line, Y4M_FRAME_MAGIC, sizeof (Y4M_FRAME_MAGIC) - 1))
+    return Y4M_ERR_MAGIC;
+  if (line[sizeof (Y4M_FRAME_MAGIC) - 1] == '\n')
+    return Y4M_OK;		/* done -- no tags:  that was the end-of-line. */
+
+  if (line[sizeof (Y4M_FRAME_MAGIC) - 1] != Y4M_DELIM[0]) {
+    return Y4M_ERR_MAGIC;	/* wasn't a space -- what was it? */
+  }
+
+  /* proceed to get the tags... (overwrite the magic) */
+  for (n = 0, p = line; n < Y4M_LINE_MAX; n++, p++) {
+    if (y4m_read (fd, p, 1))
+      return Y4M_ERR_SYSTEM;
+    if (*p == '\n') {
+      *p = '\0';		/* Replace linefeed by end of string */
+      break;
+    }
+  }
+  if (n >= Y4M_LINE_MAX)
+    return Y4M_ERR_HEADER;
+  /* non-zero on error */
+  return y4m_parse_frame_tags (line, i);
+}
+
+
+int
+y4m_write_frame_header (int fd, const y4m_frame_info_t * i)
+{
+  char s[Y4M_LINE_MAX + 1];
+  int n;
+  int err;
+
+  n = snprintf (s, sizeof (s), "%s", Y4M_FRAME_MAGIC);
+  if ((n < 0) || (n > Y4M_LINE_MAX))
+    return Y4M_ERR_HEADER;
+  if ((err = y4m_snprint_xtags (s + n, sizeof (s) - n - 1, &(i->x_tags)))
+      != Y4M_OK)
+    return err;
+  /* non-zero on error */
+  return (y4m_write (fd, s, strlen (s)) ? Y4M_ERR_SYSTEM : Y4M_OK);
+}
+
+
+
+/*************************************************************************
+ *
+ * Read/Write entire frame
+ *
+ *************************************************************************/
+
+int
+y4m_read_frame (int fd, const y4m_stream_info_t * si, y4m_frame_info_t * fi, uint8_t * const yuv[3])
+{
+  int err;
+  int w = si->width;
+  int h = si->height;
+
+  /* Read frame header */
+  if ((err = y4m_read_frame_header (fd, fi)) != Y4M_OK)
+    return err;
+  /* Read luminance scanlines */
+  if (y4m_read (fd, yuv[0], w * h))
+    return Y4M_ERR_SYSTEM;
+  /* Read chrominance scanlines */
+  if (y4m_read (fd, yuv[1], w * h / 4))
+    return Y4M_ERR_SYSTEM;
+  if (y4m_read (fd, yuv[2], w * h / 4))
+    return Y4M_ERR_SYSTEM;
+
+  return Y4M_OK;
+}
+
+
+
+
+int
+y4m_write_frame (int fd, const y4m_stream_info_t * si,
+		 const y4m_frame_info_t * fi, uint8_t * const yuv[3])
+{
+  int err;
+  int w = si->width;
+  int h = si->height;
+
+  /* Write frame header */
+  if ((err = y4m_write_frame_header (fd, fi)) != Y4M_OK)
+    return err;
+  /* Write luminance,chrominance scanlines */
+  if (y4m_write (fd, yuv[0], w * h) ||
+      y4m_write (fd, yuv[1], w * h / 4) || y4m_write (fd, yuv[2], w * h / 4))
+    return Y4M_ERR_SYSTEM;
+  return Y4M_OK;
+}
+
+
+
+/*************************************************************************
+ *
+ * Read/Write entire frame, (de)interleaved (to)from two separate fields
+ *
+ *************************************************************************/
+
+
+int
+y4m_read_fields (int fd, const y4m_stream_info_t * si, y4m_frame_info_t * fi,
+		 uint8_t * const upper_field[3], uint8_t * const lower_field[3])
+{
+  int i, y, err;
+  int width = si->width;
+  int height = si->height;
+
+  /* Read frame header */
+  if ((err = y4m_read_frame_header (fd, fi)) != Y4M_OK)
+    return err;
+  /* Read Y', Cb, and Cr planes */
+  for (i = 0; i < 3; i++) {
+    uint8_t *srctop = upper_field[i];
+    uint8_t *srcbot = lower_field[i];
+
+    /* alternately write one line from each */
+    for (y = 0; y < height; y += 2) {
+      if (y4m_read (fd, srctop, width))
+	return Y4M_ERR_SYSTEM;
+      srctop += width;
+      if (y4m_read (fd, srcbot, width))
+	return Y4M_ERR_SYSTEM;
+      srcbot += width;
+    }
+    /* for chroma, width/height are half as big */
+    if (i == 0) {
+      width /= 2;
+      height /= 2;
+    }
+  }
+  return Y4M_OK;
+}
+
+
+
+int
+y4m_write_fields (int fd, const y4m_stream_info_t * si,
+		  const y4m_frame_info_t * fi,
+		  uint8_t * const upper_field[3], uint8_t * const lower_field[3])
+{
+  int i, y, err;
+  int width = si->width;
+  int height = si->height;
+
+  /* Write frame header */
+  if ((err = y4m_write_frame_header (fd, fi)) != Y4M_OK)
+    return err;
+  /* Write Y', Cb, and Cr planes */
+  for (i = 0; i < 3; i++) {
+    uint8_t *srctop = upper_field[i];
+    uint8_t *srcbot = lower_field[i];
+
+    /* alternately write one line from each */
+    for (y = 0; y < height; y += 2) {
+      if (y4m_write (fd, srctop, width))
+	return Y4M_ERR_SYSTEM;
+      srctop += width;
+      if (y4m_write (fd, srcbot, width))
+	return Y4M_ERR_SYSTEM;
+      srcbot += width;
+    }
+    /* for chroma, width/height are half as big */
+    if (i == 0) {
+      width /= 2;
+      height /= 2;
+    }
+  }
+  return Y4M_OK;
+}
+
+
+
+/*************************************************************************
+ *
+ * Handy logging of stream info
+ *
+ *************************************************************************/
+
+void
+y4m_log_stream_info (log_level_t level, const char *prefix, const y4m_stream_info_t * i)
+{
+  char s[256];
+
+  snprintf (s, sizeof (s), "  frame size:  ");
+  if (i->width == Y4M_UNKNOWN)
+    snprintf (s + strlen (s), sizeof (s) - strlen (s), "(?)x");
+  else
+    snprintf (s + strlen (s), sizeof (s) - strlen (s), "%dx", i->width);
+  if (i->height == Y4M_UNKNOWN)
+    snprintf (s + strlen (s), sizeof (s) - strlen (s), "(?) pixels ");
+  else
+    snprintf (s + strlen (s), sizeof (s) - strlen (s), "%d pixels ", i->height);
+  if (i->framelength == Y4M_UNKNOWN)
+    snprintf (s + strlen (s), sizeof (s) - strlen (s), "(? bytes)");
+  else
+    snprintf (s + strlen (s), sizeof (s) - strlen (s), "(%d bytes)", i->framelength);
+  mjpeg_log (level, "%s%s", prefix, s);
+  if ((i->framerate.n == 0) && (i->framerate.d == 0))
+    mjpeg_log (level, "%s  frame rate:  ??? fps", prefix);
+  else
+    mjpeg_log (level, "%s  frame rate:  %d/%d fps (~%f)", prefix,
+	       i->framerate.n, i->framerate.d, (double) i->framerate.n / (double) i->framerate.d);
+  mjpeg_log (level, "%s   interlace:  %s", prefix,
+	     (i->interlace == Y4M_ILACE_NONE) ? "none/progressive" :
+	     (i->interlace == Y4M_ILACE_TOP_FIRST) ? "top-field-first" :
+	     (i->interlace == Y4M_ILACE_BOTTOM_FIRST) ? "bottom-field-first" : "anyone's guess");
+  if ((i->sampleaspect.n == 0) && (i->sampleaspect.d == 0))
+    mjpeg_log (level, "%ssample aspect ratio:  ?:?", prefix);
+  else
+    mjpeg_log (level, "%ssample aspect ratio:  %d:%d", prefix,
+	       i->sampleaspect.n, i->sampleaspect.d);
+}
+
+
+/*************************************************************************
+ *
+ * Convert error code to string
+ *
+ *************************************************************************/
+
+const char *
+y4m_strerr (int err)
+{
+  switch (err) {
+    case Y4M_OK:
+      return "no error";
+    case Y4M_ERR_RANGE:
+      return "parameter out of range";
+    case Y4M_ERR_SYSTEM:
+      return "system error (failed read/write)";
+    case Y4M_ERR_HEADER:
+      return "bad stream or frame header";
+    case Y4M_ERR_BADTAG:
+      return "unknown header tag";
+    case Y4M_ERR_MAGIC:
+      return "bad header magic";
+    case Y4M_ERR_XXTAGS:
+      return "too many xtags";
+    case Y4M_ERR_EOF:
+      return "end-of-file";
+    case Y4M_ERR_BADEOF:
+      return "stream ended unexpectedly (EOF)";
+    default:
+      return "unknown error code";
+  }
+}