[FFmpeg-devel] [PATCH] fix raw FLAC muxer extradata handling
Justin Ruggles
justin.ruggles
Sat Feb 21 02:57:09 CET 2009
Michael Niedermayer wrote:
> On Sun, Feb 15, 2009 at 07:41:26PM -0500, Justin Ruggles wrote:
>> Michael Niedermayer wrote:
>>> On Thu, Feb 12, 2009 at 10:07:52PM -0500, Justin Ruggles wrote:
>>>> Michael Niedermayer wrote:
>>>>> On Thu, Feb 12, 2009 at 08:06:25PM -0500, Justin Ruggles wrote:
>>>>>> Michael Niedermayer wrote:
>>>>>>> On Thu, Feb 12, 2009 at 07:26:33PM -0500, Justin Ruggles wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> This patch makes it so the raw FLAC muxer supports either full header or
>>>>>>>> STREAMINFO-only extradata. It fixes support for converting FLAC-in-MKV
>>>>>>>> to raw FLAC using -acodec copy.
>>>>>>>>
>>>>>>>> -Justin
>>>>>>>>
>>>>>>>> Index: libavformat/raw.c
>>>>>>>> ===================================================================
>>>>>>>> --- libavformat/raw.c (revision 17188)
>>>>>>>> +++ libavformat/raw.c (working copy)
>>>>>>>> @@ -24,6 +24,7 @@
>>>>>>>> #include "libavcodec/ac3_parser.h"
>>>>>>>> #include "libavcodec/bitstream.h"
>>>>>>>> #include "libavcodec/bytestream.h"
>>>>>>>> +#include "libavcodec/flac.h"
>>>>>>>> #include "avformat.h"
>>>>>>>> #include "raw.h"
>>>>>>>> #include "id3v2.h"
>>>>>>>> @@ -37,8 +38,12 @@
>>>>>>>> };
>>>>>>>> uint8_t *streaminfo = s->streams[0]->codec->extradata;
>>>>>>>> int len = s->streams[0]->codec->extradata_size;
>>>>>>>> - if(streaminfo != NULL && len > 0) {
>>>>>>>> - put_buffer(s->pb, header, 8);
>>>>>>>> + if (streaminfo != NULL && len >= FLAC_STREAMINFO_SIZE) {
>>>>>>>> + if (len == FLAC_STREAMINFO_SIZE) {
>>>>>>>> + put_buffer(s->pb, header, 8);
>>>>>>>> + } else if (AV_RL32(streaminfo) != MKTAG('f','L','a','C') || len < 8+FLAC_STREAMINFO_SIZE) {
>>>>>>>> + return 0;
>>>>>>> for which case is this?
>>>>>> Case when extradata does not contain only STREAMINFO, nor a valid header.
>>>>> I didnt mean that ..
>>>>> my question was more in what case, as in "a file from foogar" ...
>>>>> also considering this hypothetical case, what would the code do?
>>>>> imean not (return 0) but rather
>>>>> create valid flac, create invalid file, print error?
>>>> point taken. this would silently create invalid files for incorrectly
>>>> formatted or wrong length extradata, whether from the user or from an
>>>> invalid input file.
>>>>
>>>>>>> also the whole does not look particularely robust, i mean an extra byte at the
>>>>>>> end will make it fail silently, it would be different if there was an error
>>>>>>> message ...
>>>>>> I see your point. An alternative solution would be to only check for
>>>>>> "fLaC" and not extradata_size to determine the format of the extradata.
>>>>>> The size checks could be done in each branch to just ensure minimum
>>>>>> sizes. I can also add an error message and error return value for
>>>>>> invalid extradata. If that sounds better I can submit a new patch shortly.
>>>>> The key goal i have is
>>>>> * do not generate invalid files, at least not without a huge warning
>>>>> * when it fails it should do so with noise to asist bug analysis and debuging
>>>>> * simple, clean, fast, readable (you know, the big goals of every programmer ...)
>>>> new patch attached.
>>>>
>>>> For flac_write_header(), it fails with an error message and returns an
>>>> error value when there is no extradata or if it is too short since such
>>>> cases would always create an invalid file. It allows for the
>>>> hypothetical case you gave where the extradata is STREAMINFO plus some
>>>> extra unneeded bytes, but prints a warning message and still creates a
>>>> valid file if the first 34 bytes are valid.
>>>>
>>>> For flac_write_trailer(), no error is returned for too short or missing
>>>> metadata since rewriting the STREAMINFO is not necessary for a valid
>>>> FLAC file. A warning message is printed in such cases though.
>>>>
>>>> -Justin
>>>>
>>>> Index: libavformat/raw.c
>>>> ===================================================================
>>>> --- libavformat/raw.c (revision 17188)
>>>> +++ libavformat/raw.c (working copy)
>>>> @@ -24,6 +24,7 @@
>>>> #include "libavcodec/ac3_parser.h"
>>>> #include "libavcodec/bitstream.h"
>>>> #include "libavcodec/bytestream.h"
>>>> +#include "libavcodec/flac.h"
>>>> #include "avformat.h"
>>>> #include "raw.h"
>>>> #include "id3v2.h"
>>>> @@ -37,9 +38,23 @@
>>>> };
>>>> uint8_t *streaminfo = s->streams[0]->codec->extradata;
>>>> int len = s->streams[0]->codec->extradata_size;
>>>> - if(streaminfo != NULL && len > 0) {
>>>> + if (streaminfo != NULL && len >= FLAC_STREAMINFO_SIZE) {
>>>> + if (AV_RL32(streaminfo) != MKTAG('f','L','a','C')) {
>>>> + /* extradata contains STREAMINFO only */
>>>> + if (len != FLAC_STREAMINFO_SIZE) {
>>>> + av_log(s, AV_LOG_WARNING, "extradata contains %d bytes too many.\n",
>>>> + FLAC_STREAMINFO_SIZE-len);
>>>> + }
>>>> put_buffer(s->pb, header, 8);
>>>> + len = FLAC_STREAMINFO_SIZE;
>>>> + } else if (len < 8+FLAC_STREAMINFO_SIZE) {
>>>> + av_log(s, AV_LOG_ERROR, "extradata too small.\n");
>>>> + return -1;
>>>> + }
>>>> put_buffer(s->pb, streaminfo, len);
>>>> + } else {
>>>> + av_log(s, AV_LOG_ERROR, "extradata not found or too small.\n");
>>>> + return -1;
>>>> }
>>>> return 0;
>>>> }
>>>> @@ -51,12 +66,23 @@
>>>> int len = s->streams[0]->codec->extradata_size;
>>>> int64_t file_size;
>>>>
>>>> - if (streaminfo && len > 0 && !url_is_streamed(s->pb)) {
>>>> + if (streaminfo && len >= FLAC_STREAMINFO_SIZE && !url_is_streamed(s->pb)) {
>>> how can the first 2 conditions be false here?
>> User sets NULL or too small extradata. Our encoder would never do this.
>> And stream copy should fail at write_header() in such cases (although it
>> does not currently). But if the user does something stupid, this
>> prevents trying to write to the extradata if it's NULL or too small.
>
>> We
>> cannot rely on the extradata not changing between write_header() and
>> write_trailer() correct?
>
> extradata should generally not change, there are some rare cases like
> updating some frame count or so where it might because it cant be
> done the other way around easily but in general no extradata should
> not change and especially not significatly
>
>
>>> also i dont see how the code here really can be considered a step toward
>>> a solution.
>>> flac can be stored in many containers, we cannot duplicate these checks in
>>> every. ogg_build_flac_headers() being just one spot where this stuff is
>>> needed as well
>> I did not notice before you brought it up, but ogg_build_flac_headers()
>> needs to be changed as well, as it currently does not support full
>> header extradata. Matroska supports either type, but only checks the
>> extradata_size, not the "fLaC" signature. AFAIK, the rest that support
>> FLAC just write all the extradata as-is.
>>
>> What do you think about a shared function such as:
>>
>> enum {
>> FLAC_EXTRADATA_FORMAT_STREAMINFO = 0,
>> FLAC_EXTRADATA_FORMAT_FULL_HEADER = 1
>> }
>> /**
>> * Validate FLAC extradata.
>> * @param[out] format format of the extradata.
>> * @param[out] streaminfo_start pointer in extradata to
>> * start of STREAMINFO.
>> * @return zero for success, non-zero for error.
>> */
>> int ff_flac_validate_extradata(uint8_t *extradata,
>
> ff_is_extradata_valid()
> makes the return meaning obvious and thus means no need to read the doxy
>
> and i like the idea
Patch set attached.
[PATCH 1/5] Use a shared function to validate FLAC extradata.
[PATCH 2/5] Add support for full header extradata to raw FLAC muxer.
[PATCH 3/5] cosmetics: add a comment in flac_write_header().
[PATCH 4/5] Share the function to write a raw FLAC header and use in the
Matroska muxer.
[PATCH 5/5] cosmetics: line wrap and indentation
Thanks,
Justin
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