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

[Anatoly Nenashev]

On 02.11.2010 22:08, Michael Niedermayer wrote:
> On Tue, Nov 02, 2010 at 06:25:41AM +0300, Anatoly Nenashev wrote:
>
> [...]
>    
>> +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)) {
>> +        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;
>>      
> checking for eof after every byte read seems overkill to me
>
>
>    

Removed.

>> +
>> +            if (mxg->current_pos>  mxg->current_pos + size)
>> +                return AVERROR(ENOMEM);
>> +
>> +            mxg->buffer = av_fast_realloc(mxg->buffer,&mxg->buffer_size,
>> +                                          mxg->current_pos + size);
>> +            if (!mxg->buffer)
>> +                return AVERROR(ENOMEM);
>> +
>> +            if (size<  2) {
>> +                av_log(s, AV_LOG_ERROR, "wrong comment buffer size\n");
>> +                return AVERROR(EINVAL);
>> +            }
>>      
> checking size after using it
>    

It's moved above.

>
>    
>> +            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);
>>      
> avoidable
>
>
>    

Yes. New implementation attached.




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