[FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video
Aaron Levinson
alevinsn at aracnet.com
Fri May 12 23:19:43 EEST 2017
On 5/9/2017 11:56 AM, Michael Niedermayer wrote:
> On Thu, May 04, 2017 at 11:46:30PM -0700, Aaron Levinson wrote:
>>
>> I've provided a new version of the patch. When I created the first version of the patch on March 26th, this was the first patch that I submitted to ffmpeg, and some aspects were rough. I had indicated that the patch passed regression tests, but all I did was run "make fate", instead of "make fate SAMPLES=fate-suite/", and once I understood that I should use fate-suite, I discovered that some of the FATE tests failed with this patch. I fixed the issues with the patch, adjusted some comments, and adjusted the patch description text. I've confirmed that this patch passes all fate-suite tests for 64-bit MSVC on Windows and 64-bit gcc on Linux.
>>
>> Thanks,
>> Aaron Levinson
>>
>> ------------------------------------------------------------------------
>>
>> From 85aa383f5753795652bae015f4fe91b016f7387e Mon Sep 17 00:00:00 2001
>> From: Aaron Levinson <alevinsn at aracnet.com>
>> Date: Thu, 4 May 2017 22:54:31 -0700
>> Subject: [PATCH] ffmpeg: Fixed bug with decoding interlaced video
>>
>> Purpose: Fixed bug in ffmpeg encountered when decoding interlaced
>> video. In some cases, ffmpeg would treat it as progressive. As a
>> result of the change, the issues with interlaced video are fixed.
>>
>> Detailed description of problem: Run the following command: "ffmpeg -i
>> test8_1080i.h264 -c:v mpeg2video test8_1080i_mp2.ts". In this case,
>> test8_1080i.h264 is an H.264-encoded file with 1080i59.94
>> (interlaced). Prior to the patch, the following output is generated:
>>
>> Input #0, h264, from 'test8_1080i.h264':
>> Duration: N/A, bitrate: N/A
>> Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
>> Stream mapping:
>> Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
>> Press [q] to stop, [?] for help
>> Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
>> Metadata:
>> encoder : Lavf57.72.100
>> Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
>> Metadata:
>> encoder : Lavc57.92.100 mpeg2video
>>
>> which demonstrates the bug. The output should instead look like:
>>
>> Stream #0:0: Video: mpeg2video (Main), yuv420p(top coded first (swapped)), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
>>
>> The bug is caused by the fact that reap_filters() calls
>> init_output_stream(), which in turn calls check_init_output_file(),
>> and this is all done prior to the first call to do_video_out(). An
>> initial call to do_video_out() is necessary to populate the interlaced
>> video information to the output stream's codecpar
>> (mux_par->field_order in do_video_out()). However,
>> check_init_output_file() calls avformat_write_header() prior to the
>> initial call to do_video_out(), so field_order is populated too late,
>> and the header is written with the default field_order value,
>> progressive.
>>
>> Comments:
>>
>> -- ffmpeg.c:
>> a) Enhanced init_output_stream() to take an additional input
>> indicating whether or not check_init_output_file() should be
>> called. There are other places that call init_output_stream(), and
>> it was important to make sure that these continued to work
>> properly.
>> b) Adjusted reap_filters() such that, in the case that
>> init_output_stream() is called, it indicates that it should not
>> call check_init_output_file() in init_output_stream(). Instead, it
>> makes the call to check_init_output_file() directly, but after it
>> does the filtered frame setup and processing.
>>
>> Signed-off-by: Aaron Levinson <alevinsn at aracnet.com>
>> ---
>> ffmpeg.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 53 insertions(+), 8 deletions(-)
>>
>> diff --git a/ffmpeg.c b/ffmpeg.c
>> index e798d92277..45dbfafc04 100644
>> --- a/ffmpeg.c
>> +++ b/ffmpeg.c
>
>> @@ -1400,7 +1400,7 @@ static void do_video_stats(OutputStream *ost, int frame_size)
>> }
>> }
>>
>> -static int init_output_stream(OutputStream *ost, char *error, int error_len);
>> +static int init_output_stream(OutputStream *ost, char *error, int error_len, int do_check_output_file);
>>
>> static void finish_output_stream(OutputStream *ost)
>> {
>
>> @@ -1415,6 +1415,8 @@ static void finish_output_stream(OutputStream *ost)
>> }
>> }
>>
>> +static int check_init_output_file(OutputFile *of, int file_index);
>
> should be close to the file top, together with similar prototypes
Will do.
> [...]
>> @@ -1521,6 +1526,44 @@ static int reap_filters(int flush)
>> }
>>
>> av_frame_unref(filtered_frame);
>> +
>> + /*
>> + * It is important to call check_init_output_file() here, after
>> + * do_video_out() was called, instead of in init_output_stream(),
>> + * as was done previously.
>> + * If called from init_output_stream(), it is possible that not
>> + * everything will have been fully initialized by the time that
>> + * check_init_output_file() is called, and if
>> + * check_init_output_file() determines that all output streams
>> + * have been initialized, it will write the header. An example
>> + * of initialization that depends on do_video_out() being called
>> + * at least once is the specification of interlaced video, which
>> + * happens in do_video_out(). This is particularly relevant when
>> + * decoding--without processing a video frame, the interlaced
>> + * video setting is not propagated before the header is written,
>> + * and that causes problems.
>> + * TODO: should probably handle interlaced video differently
>> + * and not depend on it being setup in do_video_out(). Another
>> + * solution would be to set it up once by examining the input
>> + * header.
>> + */
>> + if (did_init_output_stream) {
>> + ret = check_init_output_file(of, ost->file_index);
>> + if (ret < 0)
>> + return ret;
>> + did_init_output_stream = 0;
>> + }
>> + }
>> +
>> + /*
>> + * Can't wait too long to call check_init_output_file().
>> + * Otherwise, bad things start to occur.
>> + * If didn't do it earlier, do it by the time it gets here.
>> + */
>> + if (did_init_output_stream) {
>> + ret = check_init_output_file(of, ost->file_index);
>> + if (ret < 0)
>> + return ret;
>> }
>> }
>
> you can possibly avoid did_init_output_stream by checking
> of->header_written in check_init_output_file()
I could do that, but then it would call check_init_output_file()
potentially multiple times per stream. Depending on when an output
stream is ready, it can go through reap_filters() multiple times for the
same output stream. For example, if there are two output streams, and
output stream #2 is slow to be setup, it might go through reap_filters()
multiple times for output stream #1 before it ever hits output stream
#2. If of->header_written is used to determine this, then it will call
check_init_output_file() each time. There is no benefit to calling
check_init_output_file() multiple times per stream, although it doesn't
hurt to do so as well. Also, doing this perhaps makes some assumptions
about the behavior of check_init_output_file().
>> @@ -1888,7 +1931,7 @@ static void flush_encoders(void)
>> finish_output_stream(ost);
>> }
>>
>> - ret = init_output_stream(ost, error, sizeof(error));
>> + ret = init_output_stream(ost, error, sizeof(error), 1);
>> if (ret < 0) {
>> av_log(NULL, AV_LOG_ERROR, "Error initializing output stream %d:%d -- %s\n",
>> ost->file_index, ost->index, error);
>> @@ -3396,7 +3439,7 @@ static int init_output_stream_encode(OutputStream *ost)
>> return 0;
>> }
>>
>> -static int init_output_stream(OutputStream *ost, char *error, int error_len)
>> +static int init_output_stream(OutputStream *ost, char *error, int error_len, int do_check_output_file)
>> {
>> int ret = 0;
>>
>
>> @@ -3564,9 +3607,11 @@ static int init_output_stream(OutputStream *ost, char *error, int error_len)
>>
>> ost->initialized = 1;
>>
>> - ret = check_init_output_file(output_files[ost->file_index], ost->file_index);
>> - if (ret < 0)
>> - return ret;
>> + if (do_check_output_file) {
>> + ret = check_init_output_file(output_files[ost->file_index], ost->file_index);
>> + if (ret < 0)
>> + return ret;
>> + }
>>
>> return ret;
>> }
>
> It should be cleaner to not call check_init_output_file() from
> init_output_stream() which avoids the new argument.
As discussed over IRC, I'll make that change as a separate "cosmetic"
patch and submit an additional patch for the bug fix. The two patches
should follow shortly after this e-mail. Also, I confirmed that FATE
passes on both Windows and Linux with both patches.
>
> thx
>
> PS: confirmed that interlaced information appears with this patch
> that was not there before
>
> [...]
Aaron Levinson
More information about the ffmpeg-devel
mailing list