[FFmpeg-devel] [PATCH] RTMP seek support

[Howard Chu]

Michael Niedermayer wrote:
> On Wed, Mar 31, 2010 at 05:24:49PM -0700, Howard Chu wrote:
>> Howard Chu wrote:
>>> Michael Niedermayer wrote:
>>>> removial is planed but the new API might be changed if we find the need
>>>> to change it still ...
>>
>> It seems to me that one thing that ought to be changed is that rescaling
>> the timestamp should still be done by the caller, not in read_seek2. Right
>> now each implementation of read_seek2() has to duplicate this code.
>
> if rescaling is done outside then exact seeking becomes impossible
> because rescaling implicates rounding

But that's always true, regardless. If you sepcify a seek timestamp in 
nanoseconds and the stream only supports microseconds, it is going to have to 
round anyway.

>> Index: libavformat/flvdec.c
>> ===================================================================
>> --- libavformat/flvdec.c	(revision 22713)
>> +++ libavformat/flvdec.c	(working copy)
>> @@ -442,6 +442,38 @@
>>       return ret;
>>   }
>>
>> +static int flv_read_seek(AVFormatContext *s, int stream_index,
>> +    int64_t ts, int flags)
>> +{
>> +    return av_url_read_fseek(s->pb, stream_index, ts, flags);
>> +}
>> +
>> +static int flv_read_seek2(AVFormatContext *s, int stream_index,
>> +    int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
>> +{
>> +    int ret = AVERROR_NOTSUPP;
>> +
>> +    if (url_is_streamed(s->pb)) {
>> +        if (stream_index<  0) {
>> +            AVStream *st;
>> +
>> +            stream_index = av_find_default_stream_index(s);
>> +            if (stream_index<  0)
>> +                return -1;
>> +
>> +            st = s->streams[stream_index];
>> +            // timestamp for default must be expressed in AV_TIME_BASE units
>> +            ts = av_rescale(ts, st->time_base.den,
>> +                                AV_TIME_BASE * (int64_t)st->time_base.num);
>> +        }
>> +        ret = av_url_read_fseek(s->pb, stream_index, ts, flags);
>> +    }
>> +
>> +    if (ret == AVERROR_NOTSUPP)
>> +        ret = av_seek_frame(s, stream_index, ts, flags | (ts - min_ts>  (uint64_t)(max_ts - ts) ? AVSEEK_FLAG_BACKWARD : 0));
>> +    return ret;
>> +}
>
> now i see what you meant by that this will need to be changed again
> either way this does not implement the new API correctly

It's simply based on the behavior of avformat_seek_file(). I just aimed at 
producing the same result for non-streams, while giving the protocol handler 
read_seek a chance to run.

> also you mix AVERROR_NOTSUPP with AVERROR(ENOSYS)

They are identical. AVERROR_NOTSUPP is defined to AVERROR(ENOSYS) in 
libavutil/error.h.

-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/