[FFmpeg-cvslog] r17572 - in trunk/libavcodec: mpeg12.c mpegvideo_parser.c

[Baptiste Coudurier]

On 2/25/2009 2:52 AM, Michael Niedermayer wrote:
> On Wed, Feb 25, 2009 at 01:06:02AM -0800, Baptiste Coudurier wrote:
>> On 2/24/2009 12:23 PM, cehoyos wrote:
>>> Author: cehoyos
>>> Date: Tue Feb 24 21:23:19 2009
>>> New Revision: 17572
>>>
>>> Log:
>>> Correct time_base and repeat_pict for MPEG2 video.
>>>
>>> Patch by Ivan Schreter, schreter gmx net
>>>
>>> Modified:
>>>    trunk/libavcodec/mpeg12.c
>>>    trunk/libavcodec/mpegvideo_parser.c
>>>
>>> Modified: trunk/libavcodec/mpeg12.c
>>> ==============================================================================
>>> --- trunk/libavcodec/mpeg12.c	Tue Feb 24 21:19:59 2009	(r17571)
>>> +++ trunk/libavcodec/mpeg12.c	Tue Feb 24 21:23:19 2009	(r17572)
>>> @@ -1275,7 +1275,7 @@ static int mpeg_decode_postinit(AVCodecC
>>>              av_reduce(
>>>                  &s->avctx->time_base.den,
>>>                  &s->avctx->time_base.num,
>>> -                ff_frame_rate_tab[s->frame_rate_index].num * s1->frame_rate_ext.num,
>>> +                ff_frame_rate_tab[s->frame_rate_index].num * s1->frame_rate_ext.num*2,
>>>                  ff_frame_rate_tab[s->frame_rate_index].den * s1->frame_rate_ext.den,
>>>                  1<<30);
>>>          //MPEG-2 aspect
>>>
>>> Modified: trunk/libavcodec/mpegvideo_parser.c
>>> ==============================================================================
>>> --- trunk/libavcodec/mpegvideo_parser.c	Tue Feb 24 21:19:59 2009	(r17571)
>>> +++ trunk/libavcodec/mpegvideo_parser.c	Tue Feb 24 21:23:19 2009	(r17572)
>>> @@ -81,7 +81,7 @@ static void mpegvideo_extract_headers(AV
>>>                          pc->height |=( vert_size_ext << 12);
>>>                          avctx->bit_rate += (bit_rate_ext << 18) * 400;
>>>                          avcodec_set_dimensions(avctx, pc->width, pc->height);
>>> -                        avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1);
>>> +                        avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
>>>                          avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
>>>                          avctx->codec_id = CODEC_ID_MPEG2VIDEO;
>>>                          avctx->sub_id = 2; /* forces MPEG2 */
>> I'm pretty sure this commit broke codec frame rate parsing for MPEG-2 in
>> MXF.
>>
>> Seems stream 0 codec frame rate differs from container frame rate: 50.00
>> (50/1) -> 25.00 (25/1)
>> Input #0, mxf, from 'test.mxf':
>>   Duration: 00:00:18.20, start: 0.000000, bitrate: 2086 kb/s
>>     Stream #0.0: Video: mpeg2video, yuv420p, 320x240 [PAR 1:1 DAR 4:3],
>> 104857 kb/s, 25 tbr, 25 tbn, 50 tbc
>>     Stream #0.1: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
>> At least one output file must be specified
> 
> elaborate on what is wrong please

50 tbc is wrong, should be 25.

>> Worked fine before. You can just create a .mxf with FFmpeg:
>> ffmpeg -i <file> -ar 48000 test.mxf
>>
> 
>> If I remove "* 2" everything is fine again.
> 
> cant be, durations (and thus timestamps) in mpeg2 are specified in
> half framerate units thus timebase has to be half of 1/framerate.

Well, if I remove * 2 it is 25 again.

Can you please explain how can durations and timestamps be specified in
half framerate ? Do you mean when it is coded as separate fields ?
Here one frame at 25 in PS/TS has 3600 duration, this is not half frame
rate.

-- 
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