> On Mar 15, 2018, at 17:36, James Almer <jamr...@gmail.com> wrote:
>
> On 3/14/2018 3:24 AM, Rodger Combs wrote:
>> matroska doesn't support mid-stream extradata changes
>
> How so? We update flac extradata as sent by the encoder in the last
> packet as side data.
Right, but the format itself doesn't support changing mid-stream; we handle
that case by rewriting the header.
>
>> , and rewriting
>> the same extradata already written in write_header would cause errors
>> since we previously didn't write a filler void.
>
> When would this happen? What sets both extradata in codecpar then sends
> new one as packet side data for AAC audio?
Happens after the subsequent patch ("lavf/mux: propagate extradata changes
before we call write_header to codecpar").
>
>> ---
>> libavformat/matroskaenc.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
>> index 5950b4de44..e4db5a9a1c 100644
>> --- a/libavformat/matroskaenc.c
>> +++ b/libavformat/matroskaenc.c
>> @@ -2266,7 +2266,8 @@ static int mkv_check_new_extra_data(AVFormatContext
>> *s, AVPacket *pkt)
>>
>> switch (par->codec_id) {
>> case AV_CODEC_ID_AAC:
>> - if (side_data_size && (s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
>> !mkv->is_live) {
>> + if (side_data_size && !par->extradata_size &&
>> + (s->pb->seekable & AVIO_SEEKABLE_NORMAL) && !mkv->is_live) {
>> int filler, output_sample_rate = 0;
>> int64_t curpos;
>> ret = get_aac_sample_rates(s, side_data, side_data_size,
>> &track->sample_rate,
>>
>
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