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authorStefan Kost <ensonic@users.sf.net>2010-02-03 15:07:08 +0200
committerStefan Kost <ensonic@users.sf.net>2010-02-03 15:13:30 +0200
commit6c6ea0b79b90b2d13f8e18e9115e1ae4bc347e8e (patch)
tree93704225c075eed1246c13e9b99eb476cc7269e1 /gst
parente1c1405396d830e7414b141750722c044b40d835 (diff)
downloadgstreamer-plugins-bad-6c6ea0b79b90b2d13f8e18e9115e1ae4bc347e8e.tar.gz
jpegformat: add a basic jifmuxer
The new element can chop and reassemble the markers. I implements the tagsetter and for now can serialize some tags to jpeg comments.
Diffstat (limited to 'gst')
-rw-r--r--gst/jpegformat/Makefile.am4
-rw-r--r--gst/jpegformat/gstjifmux.c514
-rw-r--r--gst/jpegformat/gstjifmux.h60
-rw-r--r--gst/jpegformat/gstjpegformat.c3
-rw-r--r--gst/jpegformat/gstjpegformat.h4
5 files changed, 581 insertions, 4 deletions
diff --git a/gst/jpegformat/Makefile.am b/gst/jpegformat/Makefile.am
index 5b85f3a0b..241ab6bd7 100644
--- a/gst/jpegformat/Makefile.am
+++ b/gst/jpegformat/Makefile.am
@@ -1,9 +1,9 @@
plugin_LTLIBRARIES = libgstjpegformat.la
-libgstjpegformat_la_SOURCES = gstjpegformat.c gstjpegparse.c
+libgstjpegformat_la_SOURCES = gstjpegformat.c gstjpegparse.c gstjifmux.c
libgstjpegformat_la_CFLAGS = $(GST_PLUGINS_BASE_CFLAGS) $(GST_CFLAGS)
libgstjpegformat_la_LIBADD = $(GST_LIBS) $(GST_BASE_LIBS)
libgstjpegformat_la_LDFLAGS = $(GST_PLUGIN_LDFLAGS)
libgstjpegformat_la_LIBTOOLFLAGS = --tag=disable-static
-noinst_HEADERS = gstjpegformat.h gstjpegparse.h
+noinst_HEADERS = gstjpegformat.h gstjpegparse.h gstjifmux.h
diff --git a/gst/jpegformat/gstjifmux.c b/gst/jpegformat/gstjifmux.c
new file mode 100644
index 000000000..b13d643e2
--- /dev/null
+++ b/gst/jpegformat/gstjifmux.c
@@ -0,0 +1,514 @@
+/* GStreamer
+ *
+ * jifmux: JPEG interchange format muxer
+ *
+ * Copyright (C) 2010 Stefan Kost <stefan.kost@nokia.com>
+ *
+ * This library 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.
+ *
+ * This library 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 this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/**
+ * SECTION:element-jifmux
+ * @short_description: JPEG interchange format writer
+ *
+ * Writes a JPEG image as JPEG/EXIF or JPEG/JFIF including various metadata.
+ *
+ * <refsect2>
+ * <title>Example launch line</title>
+ * |[
+ * gst-launch -v videotestsrc num-buffers=1 ! jpegenc ! jifmux ! filesink location=...
+ * ]|
+ * The above pipeline renders a frame, encodes to jpeg, adds metadata and writes
+ * it to disk.
+ * </refsect2>
+ */
+/*
+jpeg interchange format:
+file header : SOI, APPn{JFIF,EXIF,...}
+frame header: DQT, SOF
+scan header : {DAC,DHT},DRI,SOS
+<scan data>
+file trailer: EOI
+
+tests:
+gst-launch videotestsrc num-buffers=1 ! jpegenc ! jifmux ! filesink location=test1.jpeg
+gst-launch videotestsrc num-buffers=1 ! jpegenc ! taginject tags="comment=\"test image\"" ! jifmux ! filesink location=test2.jpeg
+*/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <string.h>
+#include <gst/base/gstbytereader.h>
+#include <gst/base/gstbytewriter.h>
+
+#include "gstjifmux.h"
+
+static GstStaticPadTemplate gst_jif_mux_src_pad_template =
+GST_STATIC_PAD_TEMPLATE ("src",
+ GST_PAD_SRC,
+ GST_PAD_ALWAYS,
+ GST_STATIC_CAPS ("image/jpeg")
+ );
+
+static GstStaticPadTemplate gst_jif_mux_sink_pad_template =
+GST_STATIC_PAD_TEMPLATE ("sink",
+ GST_PAD_SINK,
+ GST_PAD_ALWAYS,
+ GST_STATIC_CAPS ("image/jpeg")
+ );
+
+GST_DEBUG_CATEGORY_STATIC (jif_mux_debug);
+#define GST_CAT_DEFAULT jif_mux_debug
+
+typedef struct _GstJifMuxMarker
+{
+ guint8 marker;
+ guint16 size;
+
+ const guint8 *data;
+ gboolean owned;
+} GstJifMuxMarker;
+
+struct _GstJifMuxPrivate
+{
+ GstPad *srcpad;
+
+ /* list of GstJifMuxMarker */
+ GList *markers;
+ guint16 scan_size;
+ const guint8 *scan_data;
+};
+
+static void gst_jif_mux_base_init (gpointer g_class);
+static void gst_jif_mux_class_init (GstJifMuxClass * klass);
+static void gst_jif_mux_finalize (GObject * object);
+
+static void gst_jif_mux_reset (GstJifMux * self);
+static gboolean gst_jif_mux_sink_setcaps (GstPad * pad, GstCaps * caps);
+static gboolean gst_jif_mux_sink_event (GstPad * pad, GstEvent * event);
+static GstFlowReturn gst_jif_mux_chain (GstPad * pad, GstBuffer * buffer);
+
+
+static void
+gst_jif_type_init (GType type)
+{
+ static const GInterfaceInfo tag_setter_info = { NULL, NULL, NULL };
+
+ g_type_add_interface_static (type, GST_TYPE_TAG_SETTER, &tag_setter_info);
+
+ GST_DEBUG_CATEGORY_INIT (jif_mux_debug, "jifmux", 0,
+ "JPEG interchange format muxer");
+}
+
+GST_BOILERPLATE_FULL (GstJifMux, gst_jif_mux, GstElement, GST_TYPE_ELEMENT,
+ gst_jif_type_init);
+
+static void
+gst_jif_mux_base_init (gpointer g_class)
+{
+ GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);
+
+ gst_element_class_add_pad_template (element_class,
+ gst_static_pad_template_get (&gst_jif_mux_src_pad_template));
+ gst_element_class_add_pad_template (element_class,
+ gst_static_pad_template_get (&gst_jif_mux_sink_pad_template));
+ gst_element_class_set_details_simple (element_class,
+ "JPEG stream parser",
+ "Codec/Parser/Video",
+ "Parse JPEG images into single-frame buffers",
+ "Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>");
+}
+
+static void
+gst_jif_mux_class_init (GstJifMuxClass * klass)
+{
+ GObjectClass *gobject_class;
+
+ gobject_class = (GObjectClass *) klass;
+
+ g_type_class_add_private (gobject_class, sizeof (GstJifMuxPrivate));
+
+ gobject_class->finalize = gst_jif_mux_finalize;
+}
+
+static void
+gst_jif_mux_init (GstJifMux * self, GstJifMuxClass * g_class)
+{
+ GstPad *sinkpad;
+
+ self->priv = G_TYPE_INSTANCE_GET_PRIVATE (self, GST_TYPE_JIF_MUX,
+ GstJifMuxPrivate);
+
+ /* create the sink and src pads */
+ sinkpad = gst_pad_new_from_static_template (&gst_jif_mux_sink_pad_template,
+ "sink");
+ gst_pad_set_chain_function (sinkpad, GST_DEBUG_FUNCPTR (gst_jif_mux_chain));
+ gst_pad_set_setcaps_function (sinkpad,
+ GST_DEBUG_FUNCPTR (gst_jif_mux_sink_setcaps));
+ gst_pad_set_event_function (sinkpad,
+ GST_DEBUG_FUNCPTR (gst_jif_mux_sink_event));
+ gst_element_add_pad (GST_ELEMENT (self), sinkpad);
+
+ self->priv->srcpad =
+ gst_pad_new_from_static_template (&gst_jif_mux_src_pad_template, "src");
+ gst_element_add_pad (GST_ELEMENT (self), self->priv->srcpad);
+}
+
+static void
+gst_jif_mux_finalize (GObject * object)
+{
+ GstJifMux *self = GST_JIF_MUX (object);
+
+ gst_jif_mux_reset (self);
+ G_OBJECT_CLASS (parent_class)->finalize (object);
+}
+
+static gboolean
+gst_jif_mux_sink_setcaps (GstPad * pad, GstCaps * caps)
+{
+ GstJifMux *self = GST_JIF_MUX (GST_PAD_PARENT (pad));
+ GstStructure *s = gst_caps_get_structure (caps, 0);
+ const gchar *variant;
+
+ /* should be {combined (default), EXIF, JFIF} */
+ if ((variant = gst_structure_get_string (s, "variant")) != NULL) {
+ GST_INFO_OBJECT (self, "muxing to '%s'", variant);
+ /* FIXME: do we want to switch it like this or use a gobject property ? */
+ }
+
+ return TRUE;
+}
+
+static gboolean
+gst_jif_mux_sink_event (GstPad * pad, GstEvent * event)
+{
+ GstJifMux *self = GST_JIF_MUX (GST_PAD_PARENT (pad));
+ gboolean ret;
+
+ switch (GST_EVENT_TYPE (event)) {
+ case GST_EVENT_TAG:{
+ GstTagList *list;
+ GstTagSetter *setter = GST_TAG_SETTER (self);
+ const GstTagMergeMode mode = gst_tag_setter_get_tag_merge_mode (setter);
+
+ gst_event_parse_tag (event, &list);
+ gst_tag_setter_merge_tags (setter, list, mode);
+ break;
+ }
+ default:
+ break;
+ }
+ ret = gst_pad_event_default (pad, event);
+ return ret;
+}
+
+static void
+gst_jif_mux_reset (GstJifMux * self)
+{
+ GList *node;
+ GstJifMuxMarker *m;
+
+ for (node = self->priv->markers; node; node = g_list_next (node)) {
+ m = (GstJifMuxMarker *) node->data;
+
+ if (m->owned)
+ g_free ((gpointer) m->data);
+
+ g_slice_free (GstJifMuxMarker, m);
+ }
+ g_list_free (self->priv->markers);
+ self->priv->markers = NULL;
+}
+
+static GstJifMuxMarker *
+gst_jif_mux_new_marker (guint8 marker, guint16 size, const guint8 * data,
+ gboolean owned)
+{
+ GstJifMuxMarker *m = g_slice_new (GstJifMuxMarker);
+
+ m->marker = marker;
+ m->size = size;
+ m->data = data;
+ m->owned = owned;
+
+ return m;
+}
+
+static gboolean
+gst_jif_mux_parse_image (GstJifMux * self, GstBuffer * buf)
+{
+ GstByteReader reader = GST_BYTE_READER_INIT_FROM_BUFFER (buf);
+ GstJifMuxMarker *m;
+ guint8 marker;
+ guint16 size;
+ const guint8 *data;
+
+ if (!gst_byte_reader_peek_uint8 (&reader, &marker))
+ goto error;
+
+ while (marker == 0xff) {
+ if (!gst_byte_reader_skip (&reader, 1))
+ goto error;
+
+ if (!gst_byte_reader_get_uint8 (&reader, &marker))
+ goto error;
+
+ switch (marker) {
+ case RST0:
+ case RST1:
+ case RST2:
+ case RST3:
+ case RST4:
+ case RST5:
+ case RST6:
+ case RST7:
+ case SOI:
+ GST_DEBUG_OBJECT (self, "marker = %x", marker);
+ m = gst_jif_mux_new_marker (marker, 0, NULL, FALSE);
+ self->priv->markers = g_list_prepend (self->priv->markers, m);
+ break;
+ case EOI:
+ GST_DEBUG_OBJECT (self, "marker = %x", marker);
+ m = gst_jif_mux_new_marker (marker, 0, NULL, FALSE);
+ self->priv->markers = g_list_prepend (self->priv->markers, m);
+ goto done;
+ break;
+ default:
+ if (!gst_byte_reader_get_uint16_be (&reader, &size))
+ goto error;
+ if (!gst_byte_reader_get_data (&reader, size - 2, &data))
+ goto error;
+ m = gst_jif_mux_new_marker (marker, size - 2, data, FALSE);
+ self->priv->markers = g_list_prepend (self->priv->markers, m);
+
+ GST_DEBUG_OBJECT (self, "marker = %2x, size = %u", marker, size);
+ break;
+ }
+
+ if (marker == SOS) {
+ /* remaining size except EOI is scan data */
+ self->priv->scan_size = GST_BUFFER_SIZE (buf) - 4 -
+ gst_byte_reader_get_pos (&reader);
+ if (!gst_byte_reader_get_data (&reader, self->priv->scan_size,
+ &self->priv->scan_data))
+ goto error;
+
+ GST_DEBUG_OBJECT (self, "scan data, size = %u", self->priv->scan_size);
+ }
+
+ if (!gst_byte_reader_peek_uint8 (&reader, &marker))
+ goto error;
+ }
+ GST_INFO_OBJECT (self, "done parsing at 0x%x / 0x%x",
+ gst_byte_reader_get_pos (&reader), GST_BUFFER_SIZE (buf));
+
+done:
+ self->priv->markers = g_list_reverse (self->priv->markers);
+ return TRUE;
+
+error:
+ GST_WARNING_OBJECT (self,
+ "Error parsing image header (need more that %u bytes available)",
+ gst_byte_reader_get_remaining (&reader));
+ return FALSE;
+}
+
+static gboolean
+gst_jif_mux_mangle_markers (GstJifMux * self)
+{
+ gboolean modified = FALSE;
+ const GstTagList *tags;
+ GstJifMuxMarker *m;
+ GList *node, *file_hdr = NULL, *frame_hdr = NULL, *scan_hdr = NULL;
+
+ /* FIXME: implement me more
+ * - update the APP markers
+ * - put any JFIF APP0 first
+ * - the Exif APP1 next,
+ * - the XMP APP1 next,
+ * - the PSIR APP13 next,
+ * - followed by all other marker segments
+ */
+
+ /* find some reference points where we insert before/after */
+ file_hdr = self->priv->markers;
+ for (node = self->priv->markers; node; node = g_list_next (node)) {
+ m = (GstJifMuxMarker *) node->data;
+
+ switch (m->marker) {
+ case DQT:
+ case SOF0:
+ case SOF1:
+ case SOF2:
+ case SOF3:
+ case SOF5:
+ case SOF6:
+ case SOF7:
+ case SOF9:
+ case SOF10:
+ case SOF11:
+ case SOF13:
+ case SOF14:
+ case SOF15:
+ if (!frame_hdr)
+ frame_hdr = node;
+ break;
+ case DAC:
+ case DHT:
+ case DRI:
+ case SOS:
+ if (!scan_hdr)
+ scan_hdr = node;
+ break;
+ }
+ }
+
+ /* if we want combined or JFIF */
+ /* check if we don't have JFIF APP0 */
+ /* insert into self->markers list */
+ /* ensure its first */
+ /* else */
+ /* remove JFIF if exists */
+
+ /* if we want combined or EXIF */
+ /* check if we don't have EXIF APP1 */
+ /* insert into self->markers list */
+ /* else */
+ /* remove EXIF if exists */
+
+ /* add jpeg comment */
+ tags = gst_tag_setter_get_tag_list (GST_TAG_SETTER (self));
+ if (tags) {
+ gchar *str = NULL;
+
+ (void) (gst_tag_list_get_string (tags, GST_TAG_COMMENT, &str) ||
+ gst_tag_list_get_string (tags, GST_TAG_DESCRIPTION, &str) ||
+ gst_tag_list_get_string (tags, GST_TAG_TITLE, &str));
+
+ if (str) {
+ /* insert new marker into self->markers list */
+ m = gst_jif_mux_new_marker (COM, strlen (str) + 1, (const guint8 *) str,
+ TRUE);
+ /* this should go before SOS, maybe at the end of file-header */
+ self->priv->markers = g_list_insert_before (self->priv->markers,
+ frame_hdr, m);
+
+ modified = TRUE;
+ }
+ }
+ return modified;
+}
+
+static GstFlowReturn
+gst_jif_mux_recombine_image (GstJifMux * self, GstBuffer ** new_buf,
+ GstBuffer * old_buf)
+{
+ GstBuffer *buf;
+ GstByteWriter *writer;
+ GstFlowReturn fret;
+ GstJifMuxMarker *m;
+ GList *node;
+ guint size = self->priv->scan_size;
+
+ /* iterate list and collect size */
+ for (node = self->priv->markers; node; node = g_list_next (node)) {
+ m = (GstJifMuxMarker *) node->data;
+
+ /* some markers like e.g. SOI are empty */
+ if (m->size) {
+ size += 2 + m->size;
+ }
+ /* 0xff <marker> */
+ size += 2;
+ }
+ GST_INFO_OBJECT (self, "old size: %u, new size: %u",
+ GST_BUFFER_SIZE (old_buf), size);
+
+ /* allocate new buffer */
+ fret = gst_pad_alloc_buffer_and_set_caps (self->priv->srcpad,
+ GST_BUFFER_OFFSET (old_buf), size, GST_PAD_CAPS (self->priv->srcpad),
+ &buf);
+ if (fret != GST_FLOW_OK)
+ goto no_buffer;
+
+ /* copy buffer metadata */
+ gst_buffer_copy_metadata (buf, old_buf,
+ GST_BUFFER_COPY_FLAGS | GST_BUFFER_COPY_TIMESTAMPS);
+
+ /* memcopy markers */
+ writer = gst_byte_writer_new_with_buffer (buf, TRUE);
+ for (node = self->priv->markers; node; node = g_list_next (node)) {
+ m = (GstJifMuxMarker *) node->data;
+
+ gst_byte_writer_put_uint8 (writer, 0xff);
+ gst_byte_writer_put_uint8 (writer, m->marker);
+
+ GST_DEBUG_OBJECT (self, "marker = %2x, size = %u", m->marker, m->size + 2);
+
+ if (m->size) {
+ gst_byte_writer_put_uint16_be (writer, m->size + 2);
+ gst_byte_writer_put_data (writer, m->data, m->size);
+ }
+
+ if (m->marker == SOS) {
+ GST_DEBUG_OBJECT (self, "scan data, size = %u", self->priv->scan_size);
+ gst_byte_writer_put_data (writer, self->priv->scan_data,
+ self->priv->scan_size);
+ }
+ }
+ gst_byte_writer_free (writer);
+
+ *new_buf = buf;
+ return GST_FLOW_OK;
+
+no_buffer:
+ GST_WARNING_OBJECT (self, "failed to allocate output buffer, flow_ret = %s",
+ gst_flow_get_name (fret));
+ return fret;
+}
+
+static GstFlowReturn
+gst_jif_mux_chain (GstPad * pad, GstBuffer * buf)
+{
+ GstJifMux *self = GST_JIF_MUX (GST_PAD_PARENT (pad));
+ guint8 *data = GST_BUFFER_DATA (buf);
+ GstFlowReturn fret = GST_FLOW_OK;
+
+ GST_MEMDUMP ("jpeg beg", data, 64);
+ GST_MEMDUMP ("jpeg end", &data[GST_BUFFER_SIZE (buf) - 64], 64);
+
+ /* we should have received a whole picture from SOI to EOI
+ * build a list of markers */
+ if (gst_jif_mux_parse_image (self, buf)) {
+ /* modify marker list */
+ if (gst_jif_mux_mangle_markers (self)) {
+ /* the list was changed, remux */
+ GstBuffer *old = buf;
+ fret = gst_jif_mux_recombine_image (self, &buf, old);
+ gst_buffer_unref (old);
+ }
+ }
+
+ /* free the marker list */
+ gst_jif_mux_reset (self);
+
+ if (fret == GST_FLOW_OK) {
+ fret = gst_pad_push (self->priv->srcpad, buf);
+ }
+ return fret;
+}
diff --git a/gst/jpegformat/gstjifmux.h b/gst/jpegformat/gstjifmux.h
new file mode 100644
index 000000000..1522a5dc3
--- /dev/null
+++ b/gst/jpegformat/gstjifmux.h
@@ -0,0 +1,60 @@
+/* GStreamer
+ *
+ * jifmux: JPEG interchange format muxer
+ *
+ * Copyright (C) 2010 Stefan Kost <stefan.kost@nokia.com>
+ *
+ * This library 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.
+ *
+ * This library 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 this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __GST_JFIF_MUX_H__
+#define __GST_JFIF_MUX_H__
+
+#include <gst/gst.h>
+
+#include "gstjpegformat.h"
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_JIF_MUX \
+ (gst_jif_mux_get_type())
+#define GST_JIF_MUX(obj) \
+ (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_JIF_MUX,GstJifMux))
+#define GST_JIF_MUX_CLASS(klass) \
+ (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_JIF_MUX,GstJifMuxClass))
+#define GST_IS_JIF_MUX(obj) \
+ (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_JIF_MUX))
+#define GST_IS_JIF_MUX_CLASS(klass) \
+ (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_JIF_MUX))
+
+typedef struct _GstJifMux GstJifMux;
+typedef struct _GstJifMuxPrivate GstJifMuxPrivate;
+typedef struct _GstJifMuxClass GstJifMuxClass;
+
+struct _GstJifMux {
+ GstElement element;
+ GstJifMuxPrivate *priv;
+};
+
+struct _GstJifMuxClass {
+ GstElementClass parent_class;
+};
+
+GType gst_jif_mux_get_type (void);
+
+G_END_DECLS
+
+#endif /* __GST_JFIF_MUX_H__ */
diff --git a/gst/jpegformat/gstjpegformat.c b/gst/jpegformat/gstjpegformat.c
index a64a54c06..88b14f5d4 100644
--- a/gst/jpegformat/gstjpegformat.c
+++ b/gst/jpegformat/gstjpegformat.c
@@ -25,6 +25,7 @@
#endif
#include "gstjpegparse.h"
+#include "gstjifmux.h"
static gboolean
plugin_init (GstPlugin * plugin)
@@ -32,6 +33,8 @@ plugin_init (GstPlugin * plugin)
if (!gst_element_register (plugin, "jpegparse", GST_RANK_PRIMARY + 1,
GST_TYPE_JPEG_PARSE))
return FALSE;
+ if (!gst_element_register (plugin, "jifmux", GST_RANK_NONE, GST_TYPE_JIF_MUX))
+ return FALSE;
return TRUE;
}
diff --git a/gst/jpegformat/gstjpegformat.h b/gst/jpegformat/gstjpegformat.h
index 819e879f6..118dd7a09 100644
--- a/gst/jpegformat/gstjpegformat.h
+++ b/gst/jpegformat/gstjpegformat.h
@@ -67,8 +67,8 @@ G_BEGIN_DECLS
#define SOS 0xda /* Start Of Scan */
#define DHT 0xc4 /* Huffman Table(s) */
-#define DAC 0xcc
-#define DQT 0xdb /* Huffman Table(s) */
+#define DAC 0xcc /* Algorithmic Coding Table */
+#define DQT 0xdb /* Quantisation Table(s) */
#define DNL 0xdc /* Number of lines */
#define DRI 0xdd /* Restart Interval */
#define DHP 0xde /* Hierarchical progression */