[Ffmpeg-devel] [PATCH] mtv demuxer genesis

Reynaldo H. Verdejo Pinochet reynaldo
Sun Oct 8 10:04:14 CEST 2006


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.

Best regards

	Reynaldo H. Verdejo Pinochet

ps1: for a more bearable testing xperience you may consider trying
this sample instead:
http://www.mympxplayer.org/santana-im-feeling-you-mtv-format-df32.html
ps2: even I have commit rigths I dont feel like just commiting this
code without your permission, allthough it will be easier for me to
continue development while on the repo. I promise it wont break a thing
as long as you dont try it :P. No, seriously, let me know what you think
about it.
-------------- next part --------------
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	2006-10-08 03:39:35.000000000 -0400
@@ -0,0 +1,243 @@
+/*
+ * MTV (.mtv) File Demuxer
+ * Copyright (c) 2006 The ffmpeg Project
+ *
+ * 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 format file demuxer
+ * by Reynaldo H. Verdejo Pinochet (reynaldo AT opendot cl)
+ */
+
+#include "avformat.h"
+
+#define MTV_MAGIC_NUMBER 0x564d41
+#define MTV_ASUBCHUNK_SIZE 512
+#define MTV_HEADER_SIZE 512
+#define MTV_AUDIO_PADDING_SIZE 12
+
+#define NEXT_PACKET_IS_AUDIO 1    
+#define NEXT_PACKET_IS_PICTURE 2    
+
+#define LE_24(x) ((((uint8_t*)(x))[2] << 16) | (((uint8_t*)(x))[1] << 8) | \
+((uint8_t*)(x))[0])
+
+typedef struct MTVDemuxContext {
+
+    uint64_t            file_size;
+    int                 segments;
+    uint32_t            audio_identifier;
+    uint16_t            audio_br;
+    uint32_t            img_colorfmt;
+    uint8_t             img_bpp;
+    uint16_t            img_width;
+    uint16_t            img_height;
+    uint16_t            img_segment_size;
+    uint16_t            video_fps;
+    unsigned int        audio_segment_size;
+
+    int                 video_stream_index;
+    int                 audio_stream_index;
+    int64_t             video_pts;
+    int64_t             audio_packet_count;
+    uint8_t             next_packet_flag;
+
+} MTVDemuxContext;
+
+static int mtv_probe(AVProbeData *p)
+{
+    if(p->buf_size < 3)
+        return 0;
+
+    if(LE_24(&p->buf[0]) != MTV_MAGIC_NUMBER)
+        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;
+    unsigned char       data[MTV_HEADER_SIZE];
+
+    if (get_buffer(pb, data, MTV_HEADER_SIZE) != MTV_HEADER_SIZE)
+        return AVERROR_IO;
+
+    /* got header, fill data */
+
+    mtv->file_size = LE_32(&data[3]);
+    mtv->segments = LE_32(&data[7]);
+    mtv->audio_identifier = LE_24(&data[43]);
+    mtv->audio_br=data[46];
+    mtv->img_colorfmt = LE_24(&data[48]);
+    mtv->img_bpp = data[51];
+    mtv->img_width = data[52];
+    mtv->img_height = data[54];
+    mtv->img_segment_size = LE_16(&data[56]);
+    mtv->audio_segment_size = data[62] * MTV_ASUBCHUNK_SIZE;
+    mtv->video_fps = (data[46]/4) / data[62];
+  
+    /* 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, 0);
+    if(!st)
+        return AVERROR_NOMEM;
+
+    av_set_pts_info(st, 64, 1, mtv->video_fps);
+    mtv->video_stream_index = st->index;
+    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, 1);
+    if(!st)
+        return AVERROR_NOMEM;
+    
+    // av_set_pts_info(st, 33, 1, 90000);
+    mtv->audio_stream_index = st->index;
+    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;
+
+    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;
+    uint8_t *buffer, tmp;
+
+    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)
+    {
+        if(!(buffer = av_mallocz(padding)))
+            return AVERROR_NOMEM;
+
+        if(get_buffer(pb, buffer, padding) != padding)
+        {
+            av_free(buffer);
+            return AVERROR_IO;
+        }
+
+        av_free(buffer);
+
+        if((ret = av_get_packet(pb, pkt, chunk_size - padding)) != 
+        chunk_size - padding)
+            return AVERROR_IO;
+
+        pkt->stream_index = mtv->audio_stream_index;
+
+    }else
+    {
+        buffer = av_mallocz(chunk_size);
+
+        if(!buffer)
+            return AVERROR_NOMEM;
+
+        if((ret = get_buffer(pb, buffer, chunk_size)) != chunk_size)
+        {
+            av_free(buffer);
+            return AVERROR_IO;
+        }
+
+        if (av_new_packet(pkt, chunk_size))
+            return AVERROR_IO;
+        
+        /* buffer is GGGRRRR BBBBBGGG 
+         * and we need RRRRRGGG GGGBBBBB
+         * for PIX_FMT_RGB565 so here we
+         * just swap bytes as they come
+         */
+
+        for(i=0;i<chunk_size-1;i++)
+        {
+            tmp = *(buffer+i);
+            *(buffer+i) = *(buffer+i+1);
+            *(buffer+i+1) = tmp;
+        }
+
+        memcpy(pkt->data, buffer, chunk_size);
+        av_free(buffer);
+        pkt->stream_index = mtv->video_stream_index;
+    }
+
+    return(ret);
+}
+
+static int mtv_read_close(AVFormatContext *s)
+{
+    return 0;
+
+}
+
+AVInputFormat mtv_demuxer = {
+    "MTV",
+    "MTV format",
+    sizeof(MTVDemuxContext),
+    mtv_probe,
+    mtv_read_header,
+    mtv_read_packet,
+    mtv_read_close,
+};
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