yuv4mpeg2 (mjpegtools) support by Rik Snel <rsnel@cube.dyndns.org>

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@3787 b3059339-0415-0410-9bf9-f77b7e298cf2

1 files changed, 766 insertions, 0 deletions

diff --git a/libmpdemux/yuv4mpeg.c b/libmpdemux/yuv4mpeg.c
new file mode 100644
index 0000000000..c96843e86e
--- /dev/null
+++ b/libmpdemux/yuv4mpeg.c
@@ -0,0 +1,766 @@
+/*
+ *  yuv4mpeg.c:  Functions for reading and writing "new" YUV4MPEG streams
+ *
+ *  Copyright (C) 2001 Matthew J. Marjanovic <maddog@mir.com>
+ *
+ *  This file is ripped from the lavtools package (mjpeg.sourceforge.net)
+ *  Ported to mplayer by Rik Snel <snel@phys.uu.nl>
+ *
+ *  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 "mp_msg.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(stream_t *s, char *buf, size_t len)
+{
+   ssize_t n;
+
+   while (len > 0) {
+     n = stream_read(s, buf, len);
+     if (n <= 0) {
+       /* return amount left to read */
+       if (n == 0)
+	 return len;  /* n == 0 --> eof */
+       else
+	 return -len; /* n < 0 --> error */
+     }
+     buf += n;
+     len -= n;
+   }
+   return 0;
+}
+
+
+#if 0 /* not needed */
+ssize_t y4m_write(int fd, char *buf, size_t len)
+{
+   ssize_t n;
+
+   while (len > 0) {
+     n = write(fd, buf, len);
+     if (n < 0) return -len;  /* return amount left to write */
+     buf += n;
+     len -= n;
+   }
+   return 0;
+}
+#endif
+
+
+/*************************************************************************
+ *
+ * "Extra tags" handling
+ *
+ *************************************************************************/
+
+
+static char *y4m_new_xtag()
+{
+  return _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, 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, 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;
+  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(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(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(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(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(y4m_stream_info_t *si)
+{ return si->sampleaspect; }
+
+int y4m_si_get_framelength(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, 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;
+	mp_msg(MSGT_DEMUX, MSGL_WARN, "Unknown stream tag encountered:  '%s'\n", 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;
+	mp_msg(MSGT_DEMUX, MSGL_WARN, "Unknown frame tag encountered:  '%s'\n", 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(stream_t *s, 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 (y4m_read(s, 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;
+   /* 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;
+}
+
+
+#if 0
+int y4m_write_stream_header(int fd, y4m_stream_info_t *i)
+{
+  char s[Y4M_LINE_MAX+1];
+  int n;
+  int err;
+
+  y4m_ratio_reduce(&(i->framerate));
+  y4m_ratio_reduce(&(i->sampleaspect));
+  n = snprintf(s, sizeof(s), "%s W%d H%d F%d:%d I%s A%d:%d",
+	       Y4M_MAGIC,
+	       i->width,
+	       i->height,
+	       i->framerate.n, i->framerate.d,
+	       (i->interlace == Y4M_ILACE_NONE) ? "p" :
+	       (i->interlace == Y4M_ILACE_TOP_FIRST) ? "t" :
+	       (i->interlace == Y4M_ILACE_BOTTOM_FIRST) ? "b" : "?",
+	       i->sampleaspect.n, i->sampleaspect.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);
+}
+#endif
+
+
+
+
+/*************************************************************************
+ *
+ * Read/Write frame header
+ *
+ *************************************************************************/
+
+int y4m_read_frame_header(stream_t *s, 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(s, line, sizeof(Y4M_FRAME_MAGIC));
+  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_SYSTEM;
+  }
+  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(s, 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);
+}
+
+
+#if 0
+int y4m_write_frame_header(int fd, 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);
+}
+#endif
+
+
+
+/*************************************************************************
+ *
+ * Read/Write entire frame
+ *
+ *************************************************************************/
+
+int y4m_read_frame(stream_t *s, y4m_stream_info_t *si, 
+		   y4m_frame_info_t *fi, unsigned char *yuv[3])
+{
+  int err;
+  int w = si->width;
+  int h = si->height;
+  
+  /* Read frame header */
+  if ((err = y4m_read_frame_header(s, fi)) != Y4M_OK) return err;
+  /* Read luminance scanlines */
+  if (y4m_read(s, yuv[0], w*h)) return Y4M_ERR_SYSTEM;
+  /* Read chrominance scanlines */
+  if (y4m_read(s, yuv[1], w*h/4)) return Y4M_ERR_SYSTEM;
+  if (y4m_read(s, yuv[2], w*h/4)) return Y4M_ERR_SYSTEM;
+
+  return Y4M_OK;
+}
+
+
+
+#if 0
+int y4m_write_frame(int fd, y4m_stream_info_t *si, 
+		    y4m_frame_info_t *fi, unsigned char *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;
+}
+#endif
+
+
+/*************************************************************************
+ *
+ * Read/Write entire frame, (de)interleaved (to)from two separate fields
+ *
+ *************************************************************************/
+
+#if 0
+int y4m_read_fields(int fd, y4m_stream_info_t *si, y4m_frame_info_t *fi,
+                    unsigned char *upper_field[3], 
+                    unsigned char *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++) {
+    unsigned char *srctop = upper_field[i];
+    unsigned char *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, y4m_stream_info_t *si, y4m_frame_info_t *fi,
+                     unsigned char *upper_field[3], 
+                     unsigned char *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++) {
+    unsigned char *srctop = upper_field[i];
+    unsigned char *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;
+}
+#endif
+
+
+/*************************************************************************
+ *
+ * Handy logging of stream info
+ *
+ *************************************************************************/
+
+void y4m_log_stream_info(const char *prefix, 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);
+  mp_msg(MSGT_DEMUX, MSGL_V, "%s%s\n", prefix, s);
+  if ((i->framerate.n == 0) && (i->framerate.d == 0))
+    mp_msg(MSGT_DEMUX, MSGL_V, "%s  frame rate:  ??? fps\n", prefix);
+  else
+    mp_msg(MSGT_DEMUX, MSGL_V, "%s  frame rate:  %d/%d fps (~%f)\n", prefix,
+	      i->framerate.n, i->framerate.d, 
+	      (double) i->framerate.n / (double) i->framerate.d);
+  mp_msg(MSGT_DEMUX, MSGL_V, "%s   interlace:  %s\n", 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))
+    mp_msg(MSGT_DEMUX, MSGL_V, "%ssample aspect ratio:  ?:?\n", prefix);
+  else
+    mp_msg(MSGT_DEMUX, MSGL_V, "%ssample aspect ratio:  %d:%d\n", 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 "stream ended unexpectedly (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";
+  default: 
+    return "unknown error code";
+  }
+}
+
+