[FFmpeg-devel] [PATCH 2/2] MxPEG decoder

Anatoly Nenashev anatoly.nenashev
Tue Nov 2 04:25:41 CET 2010


On 02.11.2010 03:23, Stefano Sabatini wrote:
> On date Tuesday 2010-11-02 03:16:04 +0300, Anatoly Nenashev encoded:
>    
>> On 02.11.2010 01:32, Michael Niedermayer wrote:
>>      
> [...]
>    
>> diff --git a/libavformat/Makefile b/libavformat/Makefile
>> index 40adb53..ae6e05b 100644
>> --- a/libavformat/Makefile
>> +++ b/libavformat/Makefile
>> @@ -147,6 +147,7 @@ OBJS-$(CONFIG_MTV_DEMUXER)               += mtv.o
>>   OBJS-$(CONFIG_MVI_DEMUXER)               += mvi.o
>>   OBJS-$(CONFIG_MXF_DEMUXER)               += mxfdec.o mxf.o
>>   OBJS-$(CONFIG_MXF_MUXER)                 += mxfenc.o mxf.o audiointerleave.o
>> +OBJS-$(CONFIG_MXG_DEMUXER)               += mxg.o
>>   OBJS-$(CONFIG_NC_DEMUXER)                += ncdec.o
>>   OBJS-$(CONFIG_NSV_DEMUXER)               += nsvdec.o
>>   OBJS-$(CONFIG_NULL_MUXER)                += nullenc.o
>> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
>> index e35f4f8..4afbef5 100644
>> --- a/libavformat/allformats.c
>> +++ b/libavformat/allformats.c
>> @@ -142,6 +142,7 @@ void av_register_all(void)
>>       REGISTER_DEMUXER  (MVI, mvi);
>>       REGISTER_MUXDEMUX (MXF, mxf);
>>       REGISTER_MUXER    (MXF_D10, mxf_d10);
>> +    REGISTER_DEMUXER  (MXG, mxg);
>>       REGISTER_DEMUXER  (NC, nc);
>>       REGISTER_DEMUXER  (NSV, nsv);
>>       REGISTER_MUXER    (NULL, null);
>> diff --git a/libavformat/mxg.c b/libavformat/mxg.c
>> new file mode 100644
>> index 0000000..917cc47
>> --- /dev/null
>> +++ b/libavformat/mxg.c
>> @@ -0,0 +1,195 @@
>> +/*
>> + * MxPEG Clip File demuxer
>> + * Copyright (c) 2010 Anatoly Nenashev
>> + *
>> + * 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 "avio.h"
>>      
>    
>> +#include<libavutil/intreadwrite.h>
>>      
> "libavutil/intreadwrite.h"
>
> also should be listed before the local header (standard headers,
> FFmpeg headers starting from libavutil... current dir headers)
>
>    
>> +
>> +#define VIDEO_STREAM_INDEX 0
>> +#define AUDIO_STREAM_INDEX 1
>> +#define DEFAULT_PACKET_SIZE 1024
>>      
>    
>> +
>> +
>>      
> nit++: one empty line
>
>    
>> +typedef struct MXGContext {
>> +    uint8_t *buffer;
>> +    unsigned int buffer_size;
>> +    unsigned int current_pos;
>> +    uint16_t state;
>> +    int vop_found;
>> +    int64_t dts;
>> +} MXGContext;
>> +
>> +static int mxg_read_header(AVFormatContext *s, AVFormatParameters *ap)
>> +{
>> +    AVStream *video_st = 0, *audio_st = 0;
>> +    MXGContext *mxg = s->priv_data;
>> +
>> +    /* video parameters will be extracted from the compressed bitstream */
>> +    video_st = av_new_stream(s, VIDEO_STREAM_INDEX);
>> +    if (!video_st)
>> +        return AVERROR(ENOMEM);
>> +    video_st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
>> +    video_st->codec->codec_id = CODEC_ID_MXPEG;
>> +    av_set_pts_info(video_st, 64, 1, 1000000);
>> +
>> +    audio_st = av_new_stream(s, AUDIO_STREAM_INDEX);
>> +    if (!audio_st)
>> +        return AVERROR(ENOMEM);
>> +    audio_st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
>> +    audio_st->codec->codec_id = CODEC_ID_PCM_ALAW;
>> +    audio_st->codec->channels = 1;
>> +    audio_st->codec->sample_rate = 8000;
>> +    audio_st->codec->bits_per_coded_sample = 8;
>> +    audio_st->codec->block_align = 1;
>> +
>> +    mxg->buffer = av_malloc(DEFAULT_PACKET_SIZE);
>>      
>    
>> +    if (!mxg->buffer) {
>> +        av_log(s, AV_LOG_ERROR, "mxg demuxer error in av_malloc()\n");
>> +        return AVERROR(ENOMEM);
>> +    }
>>      
> for all these memory error you can skip the error message, and simply
> return ENOMEM
>
>    
>> +    mxg->buffer_size = DEFAULT_PACKET_SIZE;
>> +    mxg->current_pos = 0;
>> +    mxg->state = 0;
>> +    mxg->vop_found = 0;
>> +    mxg->dts = AV_NOPTS_VALUE;
>> +
>> +    return 0;
>> +}
>> +
>> +static int mxg_read_packet(AVFormatContext *s, AVPacket *pkt)
>> +{
>> +    int ret, size;
>> +    MXGContext *mxg = s->priv_data;
>> +
>>      
>    
>> +    while(!url_feof(s->pb)&&  !url_ferror(s->pb)) {
>>      
> nit++: while_(
>
>    
>> +        const uint8_t data = get_byte(s->pb);
>> +        unsigned int found_frame_end = 0;
>> +        mxg->state = (mxg->state<<  8) | data;
>> +        mxg->buffer[mxg->current_pos++] = data;
>> +
>> +        if (mxg->state == 0xffd9) {
>> +            found_frame_end = mxg->current_pos;
>> +        } else if (mxg->state == 0xffd8) {
>> +            if (mxg->vop_found) {
>> +                //emulating frame end
>> +                found_frame_end = mxg->current_pos - 2;
>> +                url_fseek(s->pb, -2, SEEK_CUR);
>> +            } else {
>> +                mxg->vop_found = 1;
>> +            }
>> +        } else if (mxg->state == 0xfffe) {
>> +            size = get_be16(s->pb);
>> +            if (url_feof(s->pb) || url_ferror(s->pb))
>> +                return AVERROR_EOF;
>> +
>>      
>    
>> +            if (mxg->current_pos>  mxg->current_pos + size)
>> +            {
>>      
> nit++: if (...)_{
>
>    
>> +                av_log(s, AV_LOG_ERROR, "buffer overflow\n");
>> +                return AVERROR(ENOMEM);
>> +            }
>> +            mxg->buffer = av_fast_realloc(mxg->buffer,&mxg->buffer_size,
>> +                                          mxg->current_pos + size);
>>      
>    
>> +            if (!mxg->buffer) {
>> +                av_log(s, AV_LOG_ERROR, "mxg demuxer error in av_fast_realloc()\n");
>> +                return AVERROR(ENOMEM);
>> +            }
>>      
> ditto
>
>    
>> +            if (size<  2) {
>> +                av_log(s, AV_LOG_ERROR, "wrong comment buffer size\n");
>> +                return AVERROR(EINVAL);
>> +            }
>> +            mxg->buffer[mxg->current_pos++] = size>>  8;
>> +            mxg->buffer[mxg->current_pos++] = size&  0xff;
>> +
>> +            ret = get_buffer(s->pb, mxg->buffer + mxg->current_pos, size - 2);
>> +            if (ret<  0)
>> +                return ret;
>> +            if (ret>= 16&&  !strncmp(mxg->buffer + mxg->current_pos, "MXF", 3)) {
>> +                mxg->dts = AV_RL64(mxg->buffer + mxg->current_pos + 8);
>> +            }
>> +            mxg->current_pos += ret;
>> +            mxg->state = 0;
>> +        } else if (mxg->state == 0xffed) {
>> +            mxg->current_pos -= 2;
>> +            size = get_be16(s->pb);
>> +            if (url_feof(s->pb) || url_ferror(s->pb))
>> +                return AVERROR_EOF;
>> +            if (size<= 14)
>> +                return AVERROR(EINVAL);
>> +            url_fskip(s->pb, 12);
>> +            if (url_feof(s->pb) || url_ferror(s->pb))
>> +                return AVERROR_EOF;
>> +            size -= 14;
>> +            ret = av_get_packet(s->pb, pkt, size);
>> +            if (ret<  0)
>> +                return ret;
>> +
>> +            pkt->stream_index = AUDIO_STREAM_INDEX;
>> +            mxg->state = 0;
>> +
>> +            return pkt->size;
>> +        }
>> +
>> +        if (found_frame_end) {
>> +            mxg->vop_found = 0;
>> +            mxg->current_pos = 0;
>> +            ret = av_new_packet(pkt, found_frame_end);
>> +            if (ret<  0)
>> +                return ret;
>> +            memcpy(pkt->data, mxg->buffer, found_frame_end);
>> +            pkt->stream_index = VIDEO_STREAM_INDEX;
>> +            pkt->dts = mxg->dts;
>> +            return pkt->size;
>> +        }
>> +
>> +        if (mxg->current_pos>= mxg->buffer_size) {
>> +            if (mxg->current_pos>  mxg->current_pos + DEFAULT_PACKET_SIZE) {
>> +                av_log(s, AV_LOG_ERROR, "buffer overflow\n");
>> +                return AVERROR(ENOMEM);
>> +            }
>>      
>    
>> +            mxg->buffer = av_fast_realloc(mxg->buffer,&mxg->buffer_size,
>> +                                          mxg->current_pos + DEFAULT_PACKET_SIZE);
>> +            if (!mxg->buffer) {
>> +                av_log(s, AV_LOG_ERROR, "mxg demuxer error in av_fast_realloc()\n");
>> +                return AVERROR(ENOMEM);
>>      
> ditto
>
>    
>> +            }
>> +        }
>> +    }
>> +
>> +    return AVERROR_EOF;
>> +}
>> +
>> +static int mxg_close(struct AVFormatContext *s)
>> +{
>> +    MXGContext *mxg = s->priv_data;
>> +    av_freep(&mxg->buffer);
>> +    return 0;
>> +}
>> +
>>      
>    
>> +AVInputFormat mxg_demuxer = {
>> +    "mxg",
>> +    NULL_IF_CONFIG_SMALL("MxPEG Clip File Format"),
>> +    sizeof(MXGContext),
>> +    NULL,
>> +    mxg_read_header,
>> +    mxg_read_packet,
>> +    mxg_close,
>> +    .extensions = "mxg"
>>      
> please use named fields, helps legibility and ease ABI break updates.
>    
All remarks are considered in the attached patch.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: mxg_v5.patch
Type: text/x-patch
Size: 7456 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20101102/cf9c4bf8/attachment.bin>



More information about the ffmpeg-devel mailing list