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

[Michael Niedermayer]

On Thu, Mar 11, 2010 at 11:24:11AM -0800, Baptiste Coudurier wrote:
> 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.

whichever people prefer ...

but this thread brought up a new aspect, dts vs pts
if no formats support negativ pts then we dont need a flag for that
and could just have a flag for negative dts.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope
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