[FFmpeg-devel] [PATCH] asf muxer: gracefully handle negative timestamps

[Baptiste Coudurier]

On 03/11/2010 03:44 AM, Michael Niedermayer wrote:
> On Thu, Mar 11, 2010 at 12:37:20PM +0100, Vladimir Pantelic wrote:
>> Michael Niedermayer wrote:
>>> On Thu, Mar 11, 2010 at 12:15:16PM +0100, Vladimir Pantelic wrote:
>>>>   I have one asf file that when remuxed to asf with vcodec/acodec copy for
>>>>   some reason has negative dts.
>>>>
>>>>   These negative dts end up in "sendtime" as a large integer, putting the
>>>>   send
>>>>   time in future of the payload presentation time. This is due to the fact
>>>>   that (int)asf->packet_timestamp_start is converted to (unsigned
>>>>   int)sendtime
>>>>
>>>>   Attached patch make sure that we write a sendtime of 0 in this case.
>>>>
>>>>   This fixes some complaints that M$ "Windows Media ASF View 9 Series" has
>>>>   with the generated file.
>>>
>>>>    asfenc.c |    4 ++--
>>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>>   5a18e0df6769452b2874689888dfdd832cca85dc  asf_fix_send_time.patch
>>>>   Index: libavformat/asfenc.c
>>>>   ===================================================================
>>>>   --- libavformat/asfenc.c	(revision 22465)
>>>>   +++ libavformat/asfenc.c	(working copy)
>>>>   @@ -585,7 +624,7 @@
>>>>
>>>>    static int put_payload_parsing_info(
>>>>                                    AVFormatContext *s,
>>>>   -                                unsigned int    sendtime,
>>>>   +                                int             sendtime,
>>>>                                    unsigned int    duration,
>>>>                                    int             nb_payloads,
>>>>                                    int             padsize
>>>>   @@ -626,7 +665,7 @@
>>>>        if (iLengthTypeFlags&   ASF_PPI_FLAG_PADDING_LENGTH_FIELD_IS_BYTE)
>>>>            put_byte(pb, padsize - 1);
>>>>
>>>>   -    put_le32(pb, sendtime);
>>>>   +    put_le32(pb, FFMAX(0, sendtime));
>>>
>>> muxers are not supposed to store random values
>>>
>>> id suggest
>>> 1. add a flag to muxers specifying the capability of negative dts support
>>
>> add AVFMT_POSITIVE_TIMESTAMPS to asfenc, or AVFMT_NEGATIVE_TIMESTAMPS
>> to all others?
>
> AVFMT_POSITIVE_TIMESTAMPS, id say

I believe it would be more efficient the other way around, ie adding 
AVFMT_NEGATIVE_TIMESTAMP.
Which format does support negative timestamps ?

-- 
Baptiste COUDURIER
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