[Ffmpeg-devel] [PATCH] mtv demuxer genesis

Reynaldo H. Verdejo Pinochet reynaldo
Tue Oct 10 00:09:08 CEST 2006


On Sun, Oct 08, 2006 at 04:04:14AM -0400, Reynaldo H. Verdejo Pinochet wrote:
> Hi there
> 
> Well, as some of you may already know, I have been working on
> writing an mtv demuxer. Here I present you the genesis of it. I still
> got to figure out the correct way of handling pts/index and
> seeking, Ill try to have that working soon, nonetheless you can
> already try it out playing the sample on mplayerhq's ftp.
> 
> This is my first attempt at writing a lavf demuxer so any comment
> will be more than welcome, im sure there are a lot of improvements
> and corrections to be made to the code.

Second attempt, hope to have addressed most if not all sugestions
by Aurelien, Diego and Michael. pts/index handling and seeking are still
to be worked on.

Ok to commit?

	Reynaldo
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Index: libavformat/Makefile
===================================================================
--- libavformat/Makefile	(revision 6519)
+++ libavformat/Makefile	(working copy)
@@ -59,6 +59,7 @@
 OBJS-$(CONFIG_MMF_MUXER)                 += mmf.o riff.o
 OBJS-$(CONFIG_MOV_DEMUXER)               += mov.o riff.o isom.o
 OBJS-$(CONFIG_MOV_MUXER)                 += movenc.o riff.o isom.o
+OBJS-$(CONFIG_MTV_DEMUXER)               += mtv.o
 OBJS-$(CONFIG_TGP_MUXER)                 += movenc.o riff.o isom.o
 OBJS-$(CONFIG_MP4_MUXER)                 += movenc.o riff.o isom.o
 OBJS-$(CONFIG_PSP_MUXER)                 += movenc.o riff.o isom.o
Index: libavformat/allformats.c
===================================================================
--- libavformat/allformats.c	(revision 6519)
+++ libavformat/allformats.c	(working copy)
@@ -195,6 +195,9 @@
 #ifdef CONFIG_MOV_MUXER
     av_register_output_format(&mov_muxer);
 #endif
+#ifdef CONFIG_MTV_DEMUXER
+    av_register_input_format(&mtv_demuxer);
+#endif
 #ifdef CONFIG_TGP_MUXER
     av_register_output_format(&tgp_muxer);
 #endif
Index: libavformat/allformats.h
===================================================================
--- libavformat/allformats.h	(revision 6519)
+++ libavformat/allformats.h	(working copy)
@@ -88,6 +88,7 @@
 extern AVInputFormat mpegts_demuxer;
 extern AVOutputFormat mpegts_muxer;
 extern AVOutputFormat mpjpeg_muxer;
+extern AVInputFormat mtv_demuxer;
 extern AVInputFormat mxf_demuxer;
 extern AVInputFormat nsv_demuxer;
 extern AVInputFormat nut_demuxer;
-------------- next part --------------
--- /dev/null	2006-10-03 14:00:31.500904688 -0400
+++ libavformat/mtv.c	2006-10-09 18:01:19.000000000 -0400
@@ -0,0 +1,235 @@
+/*
+ * MTV Demuxer
+ * Copyright (c) 2006 Reynaldo H. Verdejo Pinochet
+ *
+ * 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 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file mtv.c
+ * mtv demuxer.
+ */
+
+#include "avformat.h"
+#include "bswap.h"
+
+#define MTV_MAGIC_NUMBER 0x564d41
+#define MTV_ASUBCHUNK_SIZE 512
+#define MTV_HEADER_SIZE 512
+#define MTV_AUDIO_PADDING_SIZE 12
+#define AUDIO_SAMPLING_RATE 44100
+#define NEXT_PACKET_IS_AUDIO 1    
+#define NEXT_PACKET_IS_PICTURE 2    
+#define VIDEO_PACKET 0
+#define AUDIO_PACKET 1
+
+typedef struct MTVDemuxContext {
+
+    unsigned int        file_size;
+    unsigned int        segments;
+    unsigned int        audio_identifier;
+    unsigned int        audio_br;
+    unsigned int        img_colorfmt;
+    unsigned int        img_bpp;
+    unsigned int        img_width;
+    unsigned int        img_height;
+    unsigned int        img_segment_size;
+    unsigned int        video_fps;
+    unsigned int        audio_segment_size;
+
+    uint64_t            video_pts;
+    uint8_t             audio_packet_count;
+    uint8_t             next_packet_flag;
+
+} MTVDemuxContext;
+
+static int mtv_probe(AVProbeData *p)
+{
+    if(p->buf_size < 3)
+        return 0;
+
+    if(*(p->buf) != 'A' || *(p->buf+1) != 'M' || *(p->buf+2) != 'V')
+        return 0;
+
+    return AVPROBE_SCORE_MAX;
+}
+
+static int mtv_read_header(AVFormatContext *s, AVFormatParameters *ap)
+{
+    MTVDemuxContext    *mtv = s->priv_data;
+    ByteIOContext      *pb = &s->pb;
+    AVStream           *st;
+
+    if(url_fseek(pb, MTV_HEADER_SIZE, SEEK_SET) != MTV_HEADER_SIZE) 
+        return AVERROR_IO;
+
+    url_fseek(pb, 3, SEEK_SET); 
+    mtv->file_size = get_le32(pb);
+    mtv->segments = get_le32(pb);
+    url_fseek(pb, 32, SEEK_CUR);
+    mtv->audio_identifier = get_le24(pb);
+    mtv->audio_br = get_le16(pb);
+    mtv->img_colorfmt = get_le24(pb);
+    mtv->img_bpp = get_byte(pb);
+    mtv->img_width = get_le16(pb);
+    mtv->img_height = get_le16(pb);
+    mtv->img_segment_size = get_le16(pb);
+    url_fseek(pb, 4, SEEK_CUR);
+    mtv->audio_segment_size = get_le16(pb) * MTV_ASUBCHUNK_SIZE;
+    mtv->video_fps = (mtv->audio_br * MTV_ASUBCHUNK_SIZE / 4) 
+                      / mtv->audio_segment_size;
+
+    /* FIXME Add sanity check here */
+
+    /* we know first packet is audio */
+
+    mtv->next_packet_flag = NEXT_PACKET_IS_AUDIO;
+    mtv->audio_packet_count = 1;
+
+    /* all systems go! init decoders */
+
+    /* video - raw rgb565 */
+
+    st = av_new_stream(s, VIDEO_PACKET);
+    if(!st)
+        return AVERROR_NOMEM;
+
+    av_set_pts_info(st, 64, 1, mtv->video_fps);
+    st->codec->codec_type = CODEC_TYPE_VIDEO;
+    st->codec->codec_id = CODEC_ID_RAWVIDEO;
+    st->codec->width = mtv->img_width;
+    st->codec->height = mtv->img_height;
+    st->codec->bits_per_sample = mtv->img_bpp;
+    st->codec->sample_rate = mtv->video_fps;
+
+    /* audio - mp3 */
+
+    st = av_new_stream(s, AUDIO_PACKET);
+    if(!st)
+        return AVERROR_NOMEM;
+    
+    av_set_pts_info(st, 33, 1, AUDIO_SAMPLING_RATE);
+    st->codec->codec_type = CODEC_TYPE_AUDIO;
+    st->codec->codec_id = CODEC_ID_MP3;
+    st->codec->bit_rate = mtv->audio_br;
+    st->need_parsing=1;
+
+    /* Jump over header */
+
+    url_fseek(pb, MTV_HEADER_SIZE, SEEK_SET);
+    return(0);
+
+}
+
+static int mtv_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    MTVDemuxContext *mtv = s->priv_data;
+    ByteIOContext *pb = &s->pb;
+    int ret, i, padding, chunk_size;
+#ifndef WORDS_BIGENDIAN
+    uint16_t *buffer, *tmp;
+#endif
+
+    ret = i = padding = chunk_size = 0;
+
+    if(url_feof(&s->pb))
+        return AVERROR_IO;
+
+    if(mtv->next_packet_flag == NEXT_PACKET_IS_AUDIO)
+    {
+        chunk_size = MTV_ASUBCHUNK_SIZE;
+        padding = MTV_AUDIO_PADDING_SIZE;
+
+        if(mtv->audio_packet_count < 
+        mtv->audio_segment_size / MTV_ASUBCHUNK_SIZE)
+        {
+            mtv->audio_packet_count++;
+            mtv->next_packet_flag = NEXT_PACKET_IS_AUDIO;
+        }else
+        {
+            mtv->audio_packet_count = 1;
+            mtv->next_packet_flag = NEXT_PACKET_IS_PICTURE;
+        }
+
+    }else
+    {
+        chunk_size = mtv->img_segment_size;
+        mtv->audio_packet_count = 1;
+        mtv->next_packet_flag = NEXT_PACKET_IS_AUDIO;
+
+    }
+
+    if(padding)
+    {
+        url_fskip(pb, padding);
+
+        if((ret = av_get_packet(pb, pkt, chunk_size - padding)) != 
+        chunk_size - padding)
+            return AVERROR_IO;
+
+        pkt->stream_index = AUDIO_PACKET;
+
+    }else
+    {
+#ifndef WORDS_BIGENDIAN
+
+        /* buffer is GGGRRRR BBBBBGGG 
+         * and we need RRRRRGGG GGGBBBBB
+         * for PIX_FMT_RGB565 so here we
+         * just swap bytes as they come
+         */
+
+        buffer = av_malloc(chunk_size);
+
+        if(!buffer)
+            return AVERROR_NOMEM;
+
+
+        if((ret = get_buffer(pb, (uint8_t *)buffer, chunk_size)) != chunk_size)
+        {
+            av_free(buffer);
+            return AVERROR_IO;
+        }
+
+        if (av_new_packet(pkt, chunk_size))
+            return AVERROR_IO;
+        
+        tmp = pkt->data;
+
+        for(i=0;i<chunk_size/2;i++)
+        {
+            *(tmp+i) = bswap_16(*(buffer+i));
+        }
+
+        av_free(buffer);
+#else
+        if((ret = av_get_packet(pb, pkt, chunk_size)) != 
+        chunk_size - padding)
+            return AVERROR_IO
+#endif
+        pkt->stream_index = VIDEO_PACKET;
+    }
+
+    return(ret);
+}
+
+AVInputFormat mtv_demuxer = {
+    "MTV",
+    "MTV format",
+    sizeof(MTVDemuxContext),
+    mtv_probe,
+    mtv_read_header,
+    mtv_read_packet,
+};
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