[FFmpeg-devel] [PATCH] lavf/dashenc: Write media trailers when DASH trailer is written.

[Andrey Semashev]

On 11/29/18 9:27 AM, Jeyapal, Karthick wrote:
> 
> On 11/28/18 5:13 PM, Andrey Semashev wrote:
>> This commit ensures that all (potentially, long) filesystem activity is
>> performed when the user calls av_write_trailer on the DASH libavformat
>> context, not when freeing the context. Also, this defers media segment
>> deletion until after the media trailers are written.
>> ---
>>   libavformat/dashenc.c | 19 ++++++++++++++-----
>>   1 file changed, 14 insertions(+), 5 deletions(-)
>>
>> diff --git a/libavformat/dashenc.c b/libavformat/dashenc.c
>> index 6ce70e0076..e1c959dc89 100644
>> --- a/libavformat/dashenc.c
>> +++ b/libavformat/dashenc.c
>> @@ -424,8 +424,6 @@ static void dash_free(AVFormatContext *s)
>>           return;
>>       for (i = 0; i < s->nb_streams; i++) {
>>           OutputStream *os = &c->streams[i];
>> -        if (os->ctx && os->ctx_inited)
>> -            av_write_trailer(os->ctx);
>>           if (os->ctx && os->ctx->pb)
>>               ffio_free_dyn_buf(&os->ctx->pb);
>>           ff_format_io_close(s, &os->out);
>> @@ -1420,13 +1418,11 @@ static int dash_flush(AVFormatContext *s, int final, int stream)
>>           os->pos += range_length;
>>       }
>>   
>> -    if (c->window_size || (final && c->remove_at_exit)) {
>> +    if (c->window_size) {
>>           for (i = 0; i < s->nb_streams; i++) {
>>               OutputStream *os = &c->streams[i];
>>               int j;
>>               int remove = os->nb_segments - c->window_size - c->extra_window_size;
>> -            if (final && c->remove_at_exit)
>> -                remove = os->nb_segments;
> Is there any reason for deferring the delete after write_trailer.
> Because if the file is getting deleted immediately, why should we bother about write_trailer? Is it causing any issues?
> I am asking this, because the segment deletion code is getting duplicated due to this change. I am trying to avoid code duplication as much as possible.
>>               if (remove > 0) {
>>                   for (j = 0; j < remove; j++) {
>>                       char filename[1024];
>> @@ -1599,11 +1595,24 @@ static int dash_write_trailer(AVFormatContext *s)
>>       }
>>       dash_flush(s, 1, -1);
>>   
>> +    for (int i = 0; i < s->nb_streams; ++i) {
> Can we merge this loop with the below loop for deleting init segments. The "if" condition for remove_at_exit, could be moved inside the merged loop.

I usually don't like conditions on constants inside loops, but I can do 
that.

>> +        OutputStream *os = &c->streams[i];
>> +        if (os->ctx && os->ctx_inited) {
>> +            av_write_trailer(os->ctx);
>> +        }
>> +    }
>> +
>>       if (c->remove_at_exit) {
>>           char filename[1024];
>>           int i;
>>           for (i = 0; i < s->nb_streams; i++) {
>>               OutputStream *os = &c->streams[i];
>> +            for (int j = 0; j < os->nb_segments; ++j) {
>> +                snprintf(filename, sizeof(filename), "%s%s", c->dirname, os->segments[j]->file);
>> +                dashenc_delete_file(s, filename);
>> +                av_free(os->segments[j]);
>> +            }
>> +            os->nb_segments = 0;
>>               snprintf(filename, sizeof(filename), "%s%s", c->dirname, os->initfile);
>>               dashenc_delete_file(s, filename);
>>           }
>