[FFmpeg-devel] [PATCH 4/6] avformat: add argo_asf muxer

[Andreas Rheinhardt]

Zane van Iperen:
>>> +static int argo_asf_write_trailer(AVFormatContext *s)
>>> +{
>>> +    int64_t data_size, num_blocks;
>>> +
>>> +    data_size = avio_tell(s->pb) - (ASF_FILE_HEADER_SIZE + ASF_CHUNK_HEADER_SIZE);
>>> +    num_blocks = data_size / (17 * s->streams[0]->codecpar->channels);
>>> +
>>> +    av_assert0(data_size % (17 * s->streams[0]->codecpar->channels) == 0);
>>
>> You must not assert this as you have not have any check in place that
>> guarantees this.
>>
>> The comment in the demuxer and the value you assign to num_samples when
>> writing the header indicates to me that num_samples is supposed to be
>> always 32; yet there is no check for that in the demuxer and if it is a
>> value different from 32 and 33, then simply remuxing such a file can
>> trigger this assert.
>>
> 
> You're right, num_samples should always be 32. I will add a check in
> the demuxer.
> 
> The 17 comes from "control byte + (32 / 2)" (the frame size for a
> single channel), so adding that check should guarantee the assertion.
> 

Why? The packets sent to this muxer need not originate from the demuxer
via remuxing or from the encoder that you are about to add.

- Andreas