[Ffmpeg-devel] [PATCH] THP Demuxer (Summer of Code qualification task)

Marco Gerards mgerards
Fri Mar 30 01:45:11 CEST 2007


Michael Niedermayer <michaelni at gmx.at> writes:


Hi,

>> Here is a patch (sent inline) to add a THP demuxer to ffmpeg.  I've
>> also changed the MPJEG decoder so it can play THP movies.  This is a
>> qualification task for Google Summer of Code 2007.
>> 
>> It perfectly plays back the samples that can be found on the ffmpeg
>> website.  Unfortunately these samples come without audio.  Because of
>> this I haven't implemented audio support yet.  I hope someone can send
>> me a sample that includes audio.  In that case I will implement this
>> as well.
>> 
>> If I can do something to improve my code or to add something that is
>> missing, please tell me.

[...]

> tabs are forbidden in svn
> additionally cosmetic changes and functional changes must be in seperate
> patches, that is dont change whitespace or indention just add the 
> if (avctx->codec_id != CODEC_ID_THP){ ... } in the first patch
> and fix the indention (and only the indention) in a second patch
> this makes reviewing patches (and commits on svnlog) much easier

Ok.  I have fixed this.

>
> [...]
>> Index: libavcodec/avcodec.h
>> ===================================================================
>> --- libavcodec/avcodec.h        (revision 8540)
>> +++ libavcodec/avcodec.h        (working copy)
>> @@ -64,6 +64,7 @@
>>      CODEC_ID_RV20,
>>      CODEC_ID_MJPEG,
>>      CODEC_ID_MJPEGB,
>> +    CODEC_ID_THP,
>>      CODEC_ID_LJPEG,
>
> read the comment at the top of this CODEC_ID list!
> you cannot add new codec_ids at random places this breaks the ABI

Fixed.  I have added the codec id to the end of the list.


> [...]
>> +  for (i = 0; i < thp->compcount; i++) {
>> +      if (thp->components[i] == 0) {
>
>> +          if (thp->vst != 0)
>> +             break;
>
> why do you discard a second video stream?

Because the documentation doesn't mention this possibility.  And I
doubt it will be used in reality.  Do you think this is important and
are there samples which I can use to test this?

[...]

I also fixed all other things you commented on, see the new patch
below.  The most mistakes I made were because I copied a lot from
other demuxers.  Is there any good documentation available about how
to do all this correctly instead of looking at other demuxers?

--
Marco




Index: libavcodec/mjpeg.c
===================================================================
--- libavcodec/mjpeg.c	(revision 8550)
+++ libavcodec/mjpeg.c	(working copy)
@@ -2044,6 +2044,9 @@
                         uint8_t x = *(src++);
 
                         *(dst++) = x;
+                        if (avctx->codec_id != CODEC_ID_THP)
+			{
+
                         if (x == 0xff)
                         {
                             while(src<buf_end && x == 0xff)
@@ -2054,6 +2057,7 @@
                             else if (x)
                                 break;
                         }
+			}
                     }
                     init_get_bits(&s->gb, s->buffer, (dst - s->buffer)*8);
 
@@ -2583,6 +2587,19 @@
     NULL
 };
 
+AVCodec thp_decoder = {
+    "thp",
+    CODEC_TYPE_VIDEO,
+    CODEC_ID_THP,
+    sizeof(MJpegDecodeContext),
+    mjpeg_decode_init,
+    NULL,
+    mjpeg_decode_end,
+    mjpeg_decode_frame,
+    CODEC_CAP_DR1,
+    NULL
+};
+
 AVCodec mjpegb_decoder = {
     "mjpegb",
     CODEC_TYPE_VIDEO,
Index: libavcodec/allcodecs.c
===================================================================
--- libavcodec/allcodecs.c	(revision 8540)
+++ libavcodec/allcodecs.c	(working copy)
@@ -130,6 +130,7 @@
     REGISTER_DECODER(SVQ3, svq3);
     REGISTER_ENCDEC (TARGA, targa);
     REGISTER_DECODER(THEORA, theora);
+    REGISTER_DECODER(THP, thp);
     REGISTER_DECODER(TIERTEXSEQVIDEO, tiertexseqvideo);
     REGISTER_DECODER(TIFF, tiff);
     REGISTER_DECODER(TRUEMOTION1, truemotion1);
Index: libavcodec/avcodec.h
===================================================================
--- libavcodec/avcodec.h	(revision 8540)
+++ libavcodec/avcodec.h	(working copy)
@@ -255,6 +255,8 @@
 
     CODEC_ID_MPEG2TS= 0x20000, /* _FAKE_ codec to indicate a raw MPEG2 transport
                          stream (only used by libavformat) */
+
+    CODEC_ID_THP
 };
 
 #if LIBAVCODEC_VERSION_INT < ((52<<16)+(0<<8)+0)
@@ -2329,6 +2331,7 @@
 extern AVCodec svq3_decoder;
 extern AVCodec targa_decoder;
 extern AVCodec theora_decoder;
+extern AVCodec thp_decoder;
 extern AVCodec tiertexseqvideo_decoder;
 extern AVCodec tiff_decoder;
 extern AVCodec truemotion1_decoder;
Index: libavformat/thp.c
===================================================================
--- libavformat/thp.c	(revision 0)
+++ libavformat/thp.c	(revision 0)
@@ -0,0 +1,165 @@
+/*
+ * THP Demuxer
+ * Copyright (c) 2007 Marco Gerards.
+ *
+ * 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 "avformat.h"
+#include "allformats.h"
+
+typedef struct ThpDemuxContext {
+    int              version;
+    int              first_frame;
+    int              first_framesz;
+    int              last_frame;
+    int              compoff;
+    int              framecnt;
+    AVRational       fps;
+    int              frame;
+    int              next_frame;
+    int              next_framesz;
+    int              video_stream_index;
+    int              compcount;
+    unsigned char    components[16];
+    AVStream*        vst;
+} ThpDemuxContext;
+
+
+static int thp_probe(AVProbeData *p)
+{
+    /* check file header */
+    if (p->buf_size < 4)
+        return 0;
+
+    if (AV_RL32(p->buf) == MKTAG('T', 'H', 'P', '\0'))
+        return AVPROBE_SCORE_MAX;
+    else
+        return 0;
+}
+
+static int thp_read_header(AVFormatContext *s,
+			   AVFormatParameters *ap)
+{
+  ThpDemuxContext *thp = s->priv_data;
+  AVStream *st;
+  ByteIOContext *pb = &s->pb;
+  int i;
+
+  /* Read the file header.  */
+
+                         get_be32(pb); /* Skip Magic.  */
+  thp->version         = get_be32(pb);
+
+                         get_be32(pb); /* Max buf size.  */
+                         get_be32(pb); /* Max samples.  */
+
+  thp->fps             = av_d2q(av_int2flt(get_be32(pb)), INT_MAX);
+  thp->framecnt        = get_be32(pb);
+  thp->first_framesz   = get_be32(pb);
+                         get_be32(pb); /* Data size.  */
+
+  thp->compoff         = get_be32(pb);
+                         get_be32(pb); /* offsetDataOffset.  */
+  thp->first_frame     = get_be32(pb);
+  thp->last_frame      = get_be32(pb);
+
+  thp->next_framesz    = thp->first_framesz;
+  thp->next_frame      = thp->first_frame;
+
+  /* Read the component structure.  */
+  url_fseek (pb, thp->compoff, SEEK_SET);
+  thp->compcount       = get_be32(pb);
+
+  /* Read the list of component types.  */
+  get_buffer(pb, thp->components, 16);
+
+  for (i = 0; i < thp->compcount; i++) {
+      if (thp->components[i] == 0) {
+	  if (thp->vst != 0)
+	     break;
+
+	  /* Video component.  */
+	  st = av_new_stream(s, 0);
+	  if (!st)
+	     return AVERROR_NOMEM;
+
+	  /* The denominator and numerator are switched because 1/fps
+	     is required.  */
+	  av_set_pts_info(st, 64, thp->fps.den, thp->fps.num);
+	  st->codec->codec_type = CODEC_TYPE_VIDEO;
+	  st->codec->codec_id = CODEC_ID_THP;
+	  st->codec->codec_tag = 0;  /* no fourcc */
+	  st->codec->width = get_be32(pb);
+	  st->codec->height = get_be32(pb);
+	  st->codec->sample_rate = av_q2d(thp->fps);
+	  thp->vst = st;
+	  thp->video_stream_index = st->index;
+
+	  if (thp->version == 0x11000)
+	     get_be32(pb); /* Unknown.  */
+	}
+      else if (thp->components[i] == 1) {
+         /* XXX: Required for audio playback.  */
+      }
+    }
+
+  return 0;
+}
+
+static int thp_read_packet(AVFormatContext *s,
+                            AVPacket *pkt)
+{
+    ThpDemuxContext *thp = s->priv_data;
+    ByteIOContext *pb = &s->pb;
+    int size;
+    int ret;
+
+    /* Terminate when last frame is reached.  */
+    if (thp->frame >= thp->framecnt)
+       return AVERROR_IO;
+
+    url_fseek(pb, thp->next_frame, SEEK_SET);
+
+    /* Locate the next frame and read out its size.  */
+    thp->next_frame += thp->next_framesz;
+    thp->next_framesz = get_be32(pb);
+
+                        get_be32(pb); /* Previous total size.  */
+    size              = get_be32(pb); /* Total size of this frame.  */
+
+    ret = av_get_packet(pb, pkt, size);
+    if (ret != size) {
+       av_free_packet(pkt);
+       return AVERROR_IO;
+    }
+
+    pkt->stream_index = thp->video_stream_index;
+    thp->frame++;
+
+    return 0;
+}
+
+AVInputFormat thp_demuxer = {
+    "tph",
+    "TPH",
+    sizeof(ThpDemuxContext),
+    thp_probe,
+    thp_read_header,
+    thp_read_packet
+};
Index: libavformat/Makefile
===================================================================
--- libavformat/Makefile	(revision 8540)
+++ libavformat/Makefile	(working copy)
@@ -120,6 +120,7 @@
 OBJS-$(CONFIG_SOL_DEMUXER)               += sol.o
 OBJS-$(CONFIG_SWF_DEMUXER)               += swf.o
 OBJS-$(CONFIG_SWF_MUXER)                 += swf.o
+OBJS-$(CONFIG_THP_DEMUXER)               += thp.o
 OBJS-$(CONFIG_TIERTEXSEQ_DEMUXER)        += tiertexseq.o
 OBJS-$(CONFIG_TTA_DEMUXER)               += tta.o
 OBJS-$(CONFIG_V4L2_DEMUXER)              += v4l2.o
Index: libavformat/allformats.c
===================================================================
--- libavformat/allformats.c	(revision 8540)
+++ libavformat/allformats.c	(working copy)
@@ -142,6 +142,7 @@
     REGISTER_MUXDEMUX(SWF, swf);
     REGISTER_MUXER   (TG2, tg2);
     REGISTER_MUXER   (TGP, tgp);
+    REGISTER_DEMUXER (THP, thp);
     REGISTER_DEMUXER (TIERTEXSEQ, tiertexseq);
     REGISTER_DEMUXER (TTA, tta);
     REGISTER_DEMUXER (V4L2, v4l2);
Index: libavformat/allformats.h
===================================================================
--- libavformat/allformats.h	(revision 8540)
+++ libavformat/allformats.h	(working copy)
@@ -168,6 +168,7 @@
 extern AVInputFormat yuv4mpegpipe_demuxer;
 extern AVInputFormat tiertexseq_demuxer;
 extern AVInputFormat x11_grab_device_demuxer;
+extern AVInputFormat thp_demuxer;
 
 /* raw.c */
 int pcm_read_seek(AVFormatContext *s,





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